diff --git a/gemi_invoice/lib/data/product_master.dart b/gemi_invoice/lib/data/product_master.dart
new file mode 100644
index 0000000..0fa8b9d
--- /dev/null
+++ b/gemi_invoice/lib/data/product_master.dart
@@ -0,0 +1,99 @@
+import '../models/invoice_models.dart';
+
+/// 商品情報を管理するモデル
+/// 将来的な Odoo 同期を見据えて、外部ID（odooId）を保持できるように設計
+class Product {
+  final String id;             // ローカル管理用のID
+  final int? odooId;           // Odoo上の product.product ID (nullの場合は未同期)
+  final String name;           // 商品名
+  final int defaultUnitPrice;  // 標準単価
+  final String? category;      // カテゴリ
+
+  const Product({
+    required this.id,
+    this.odooId,
+    required this.name,
+    required this.defaultUnitPrice,
+    this.category,
+  });
+
+  /// InvoiceItem への変換
+  InvoiceItem toInvoiceItem({int quantity = 1}) {
+    return InvoiceItem(
+      description: name,
+      quantity: quantity,
+      unitPrice: defaultUnitPrice,
+    );
+  }
+
+  /// 状態更新のためのコピーメソッド
+  Product copyWith({
+    String? id,
+    int? odooId,
+    String? name,
+    int? defaultUnitPrice,
+    String? category,
+  }) {
+    return Product(
+      id: id ?? this.id,
+      odooId: odooId ?? this.odooId,
+      name: name ?? this.name,
+      defaultUnitPrice: defaultUnitPrice ?? this.defaultUnitPrice,
+      category: category ?? this.category,
+    );
+  }
+
+  /// JSON変換 (ローカル保存・Odoo同期用)
+  Map<String, dynamic> toJson() {
+    return {
+      'id': id,
+      'odoo_id': odooId,
+      'name': name,
+      'default_unit_price': defaultUnitPrice,
+      'category': category,
+    };
+  }
+
+  /// JSONからモデルを生成
+  factory Product.fromJson(Map<String, dynamic> json) {
+    return Product(
+      id: json['id'],
+      odooId: json['odoo_id'],
+      name: json['name'],
+      defaultUnitPrice: json['default_unit_price'],
+      category: json['category'],
+    );
+  }
+}
+
+/// 商品マスターのテンプレートデータ
+class ProductMaster {
+  static const List<Product> products = [
+    Product(id: 'S001', name: 'システム開発費', defaultUnitPrice: 500000, category: '開発'),
+    Product(id: 'S002', name: '保守・メンテナンス費', defaultUnitPrice: 50000, category: '運用'),
+    Product(id: 'S003', name: '技術コンサルティング', defaultUnitPrice: 100000, category: '開発'),
+    Product(id: 'G001', name: 'ライセンス料 (Pro)', defaultUnitPrice: 15000, category: '製品'),
+    Product(id: 'G002', name: '初期導入セットアップ', defaultUnitPrice: 30000, category: '製品'),
+    Product(id: 'M001', name: 'ハードウェア一式', defaultUnitPrice: 250000, category: '物品'),
+    Product(id: 'Z001', name: '諸経費', defaultUnitPrice: 5000, category: 'その他'),
+  ];
+
+  /// カテゴリ一覧の取得
+  static List<String> get categories {
+    return products.map((p) => p.category ?? 'その他').toSet().toList();
+  }
+
+  /// カテゴリ別の商品取得
+  static List<Product> getProductsByCategory(String category) {
+    return products.where((p) => (p.category ?? 'その他') == category).toList();
+  }
+
+  /// 名前またはIDで検索
+  static List<Product> search(String query) {
+    final q = query.toLowerCase();
+    return products.where((p) =>
+      p.name.toLowerCase().contains(q) ||
+      p.id.toLowerCase().contains(q)
+    ).toList();
+  }
+}
diff --git a/gemi_invoice/lib/models/customer_model.dart b/gemi_invoice/lib/models/customer_model.dart
new file mode 100644
index 0000000..2197344
--- /dev/null
+++ b/gemi_invoice/lib/models/customer_model.dart
@@ -0,0 +1,87 @@
+import 'package:intl/intl.dart';
+
+/// 顧客情報を管理するモデル
+/// 将来的な Odoo 同期を見据えて、外部ID（odooId）を保持できるように設計
+class Customer {
+  final String id;             // ローカル管理用のID
+  final int? odooId;           // Odoo上の res.partner ID (nullの場合は未同期)
+  final String displayName;     // 電話帳からの表示名（検索用バッファ）
+  final String formalName;      // 請求書に記載する正式名称（株式会社〜 など）
+  final String? zipCode;        // 郵便番号
+  final String? address;        // 住所
+  final String? department;     // 部署名
+  final String? title;          // 敬称 (様、御中など。デフォルトは御中)
+  final DateTime lastUpdatedAt; // 最終更新日時
+
+  Customer({
+    required this.id,
+    this.odooId,
+    required this.displayName,
+    required this.formalName,
+    this.zipCode,
+    this.address,
+    this.department,
+    this.title = '御中',
+    DateTime? lastUpdatedAt,
+  }) : this.lastUpdatedAt = lastUpdatedAt ?? DateTime.now();
+
+  /// 請求書表示用のフルネームを取得
+  String get invoiceName => department != null && department!.isNotEmpty
+      ? "$formalName\n$department $title"
+      : "$formalName $title";
+
+  /// 状態更新のためのコピーメソッド
+  Customer copyWith({
+    String? id,
+    int? odooId,
+    String? displayName,
+    String? formalName,
+    String? zipCode,
+    String? address,
+    String? department,
+    String? title,
+    DateTime? lastUpdatedAt,
+  }) {
+    return Customer(
+      id: id ?? this.id,
+      odooId: odooId ?? this.odooId,
+      displayName: displayName ?? this.displayName,
+      formalName: formalName ?? this.formalName,
+      zipCode: zipCode ?? this.zipCode,
+      address: address ?? this.address,
+      department: department ?? this.department,
+      title: title ?? this.title,
+      lastUpdatedAt: lastUpdatedAt ?? DateTime.now(),
+    );
+  }
+
+  /// JSON変換 (ローカル保存・Odoo同期用)
+  Map<String, dynamic> toJson() {
+    return {
+      'id': id,
+      'odoo_id': odooId,
+      'display_name': displayName,
+      'formal_name': formalName,
+      'zip_code': zipCode,
+      'address': address,
+      'department': department,
+      'title': title,
+      'last_updated_at': lastUpdatedAt.toIso8601String(),
+    };
+  }
+
+  /// JSONからモデルを生成
+  factory Customer.fromJson(Map<String, dynamic> json) {
+    return Customer(
+      id: json['id'],
+      odooId: json['odoo_id'],
+      displayName: json['display_name'],
+      formalName: json['formal_name'],
+      zipCode: json['zip_code'],
+      address: json['address'],
+      department: json['department'],
+      title: json['title'] ?? '御中',
+      lastUpdatedAt: DateTime.parse(json['last_updated_at']),
+    );
+  }
+}
diff --git a/gemi_invoice/lib/models/invoice_models.dart b/gemi_invoice/lib/models/invoice_models.dart
index a672128..3989c70 100644
--- a/gemi_invoice/lib/models/invoice_models.dart
+++ b/gemi_invoice/lib/models/invoice_models.dart
@@ -1,4 +1,5 @@
 import 'package:intl/intl.dart';
+import 'customer_model.dart';
 
 /// 請求書の各明細行を表すモデル
 class InvoiceItem {
@@ -27,11 +28,29 @@ class InvoiceItem {
       unitPrice: unitPrice ?? this.unitPrice,
     );
   }
+
+  // JSON変換
+  Map<String, dynamic> toJson() {
+    return {
+      'description': description,
+      'quantity': quantity,
+      'unit_price': unitPrice,
+    };
+  }
+
+  // JSONから復元
+  factory InvoiceItem.fromJson(Map<String, dynamic> json) {
+    return InvoiceItem(
+      description: json['description'] as String,
+      quantity: json['quantity'] as int,
+      unitPrice: json['unit_price'] as int,
+    );
+  }
 }
 
 /// 請求書全体を管理するモデル
 class Invoice {
-  String clientName;
+  Customer customer; // 顧客情報
   DateTime date;
   List<InvoiceItem> items;
   String? filePath; // 保存されたPDFのパス
@@ -39,7 +58,7 @@ class Invoice {
   String? notes; // 備考
 
   Invoice({
-    required this.clientName,
+    required this.customer,
     required this.date,
     required this.items,
     this.filePath,
@@ -47,6 +66,9 @@ class Invoice {
     this.notes,
   }) : invoiceNumber = invoiceNumber ?? DateFormat('yyyyMMdd-HHmm').format(date);
 
+  // 互換性のためのゲッター
+  String get clientName => customer.formalName;
+
   // 税抜合計金額
   int get subtotal {
     return items.fold(0, (sum, item) => sum + item.subtotal);
@@ -64,7 +86,7 @@ class Invoice {
 
   // 状態更新のためのコピーメソッド
   Invoice copyWith({
-    String? clientName,
+    Customer? customer,
     DateTime? date,
     List<InvoiceItem>? items,
     String? filePath,
@@ -72,7 +94,7 @@ class Invoice {
     String? notes,
   }) {
     return Invoice(
-      clientName: clientName ?? this.clientName,
+      customer: customer ?? this.customer,
       date: date ?? this.date,
       items: items ?? this.items,
       filePath: filePath ?? this.filePath,
@@ -81,13 +103,43 @@ class Invoice {
     );
   }
 
-  // CSV形式への変換 (将来的なCSV編集用)
+  // CSV形式への変換
   String toCsv() {
     StringBuffer sb = StringBuffer();
+    sb.writeln("Customer,${customer.formalName}");
+    sb.writeln("Invoice Number,$invoiceNumber");
+    sb.writeln("Date,${DateFormat('yyyy/MM/dd').format(date)}");
+    sb.writeln("");
     sb.writeln("Description,Quantity,UnitPrice,Subtotal");
     for (var item in items) {
       sb.writeln("${item.description},${item.quantity},${item.unitPrice},${item.subtotal}");
     }
     return sb.toString();
   }
+
+  // JSON変換 (データベース保存用)
+  Map<String, dynamic> toJson() {
+    return {
+      'customer': customer.toJson(),
+      'date': date.toIso8601String(),
+      'items': items.map((item) => item.toJson()).toList(),
+      'file_path': filePath,
+      'invoice_number': invoiceNumber,
+      'notes': notes,
+    };
+  }
+
+  // JSONから復元 (データベース読み込み用)
+  factory Invoice.fromJson(Map<String, dynamic> json) {
+    return Invoice(
+      customer: Customer.fromJson(json['customer'] as Map<String, dynamic>),
+      date: DateTime.parse(json['date'] as String),
+      items: (json['items'] as List)
+          .map((i) => InvoiceItem.fromJson(i as Map<String, dynamic>))
+          .toList(),
+      filePath: json['file_path'] as String?,
+      invoiceNumber: json['invoice_number'] as String,
+      notes: json['notes'] as String?,
+    );
+  }
 }
diff --git a/gemi_invoice/lib/screens/customer_picker_modal.dart b/gemi_invoice/lib/screens/customer_picker_modal.dart
new file mode 100644
index 0000000..5f37e3c
--- /dev/null
+++ b/gemi_invoice/lib/screens/customer_picker_modal.dart
@@ -0,0 +1,308 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_contacts/flutter_contacts.dart';
+import 'package:uuid/uuid.dart';
+import '../models/customer_model.dart';
+
+/// 顧客マスターからの選択、登録、編集、削除を行うモーダル
+class CustomerPickerModal extends StatefulWidget {
+  final List<Customer> existingCustomers;
+  final Function(Customer) onCustomerSelected;
+  final Function(Customer)? onCustomerDeleted; // 削除通知用（オプション）
+
+  const CustomerPickerModal({
+    Key? key,
+    required this.existingCustomers,
+    required this.onCustomerSelected,
+    this.onCustomerDeleted,
+  }) : super(key: key);
+
+  @override
+  State<CustomerPickerModal> createState() => _CustomerPickerModalState();
+}
+
+class _CustomerPickerModalState extends State<CustomerPickerModal> {
+  String _searchQuery = "";
+  List<Customer> _filteredCustomers = [];
+  bool _isImportingFromContacts = false;
+
+  @override
+  void initState() {
+    super.initState();
+    _filteredCustomers = widget.existingCustomers;
+  }
+
+  void _filterCustomers(String query) {
+    setState(() {
+      _searchQuery = query.toLowerCase();
+      _filteredCustomers = widget.existingCustomers.where((customer) {
+        return customer.formalName.toLowerCase().contains(_searchQuery) ||
+            customer.displayName.toLowerCase().contains(_searchQuery);
+      }).toList();
+    });
+  }
+
+  /// 電話帳から取り込んで新規顧客として登録・編集するダイアログ
+  Future<void> _importFromPhoneContacts() async {
+    setState(() => _isImportingFromContacts = true);
+    try {
+      if (await FlutterContacts.requestPermission(readonly: true)) {
+        final contacts = await FlutterContacts.getContacts();
+        if (!mounted) return;
+        setState(() => _isImportingFromContacts = false);
+
+        final Contact? selectedContact = await showModalBottomSheet<Contact>(
+          context: context,
+          isScrollControlled: true,
+          builder: (context) => _PhoneContactListSelector(contacts: contacts),
+        );
+
+        if (selectedContact != null) {
+          _showCustomerEditDialog(
+            displayName: selectedContact.displayName,
+            initialFormalName: selectedContact.displayName,
+          );
+        }
+      }
+    } catch (e) {
+      setState(() => _isImportingFromContacts = false);
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(content: Text("電話帳の取得に失敗しました: $e")),
+      );
+    }
+  }
+
+  /// 顧客情報の編集・登録ダイアログ
+  void _showCustomerEditDialog({
+    required String displayName,
+    required String initialFormalName,
+    Customer? existingCustomer,
+  }) {
+    final formalNameController = TextEditingController(text: initialFormalName);
+    final departmentController = TextEditingController(text: existingCustomer?.department ?? "");
+    final addressController = TextEditingController(text: existingCustomer?.address ?? "");
+
+    showDialog(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: Text(existingCustomer == null ? "顧客の新規登録" : "顧客情報の編集"),
+        content: SingleChildScrollView(
+          child: Column(
+            mainAxisSize: MainAxisSize.min,
+            children: [
+              Text("電話帳名: $displayName", style: const TextStyle(fontSize: 12, color: Colors.grey)),
+              const SizedBox(height: 16),
+              TextField(
+                controller: formalNameController,
+                decoration: const InputDecoration(
+                  labelText: "請求書用 正式名称",
+                  hintText: "株式会社 〇〇 など",
+                  border: OutlineInputBorder(),
+                ),
+              ),
+              const SizedBox(height: 12),
+              TextField(
+                controller: departmentController,
+                decoration: const InputDecoration(
+                  labelText: "部署名",
+                  border: OutlineInputBorder(),
+                ),
+              ),
+              const SizedBox(height: 12),
+              TextField(
+                controller: addressController,
+                decoration: const InputDecoration(
+                  labelText: "住所",
+                  border: OutlineInputBorder(),
+                ),
+              ),
+            ],
+          ),
+        ),
+        actions: [
+          TextButton(onPressed: () => Navigator.pop(context), child: const Text("キャンセル")),
+          ElevatedButton(
+            onPressed: () {
+              final updatedCustomer = existingCustomer?.copyWith(
+                    formalName: formalNameController.text.trim(),
+                    department: departmentController.text.trim(),
+                    address: addressController.text.trim(),
+                  ) ??
+                  Customer(
+                    id: const Uuid().v4(),
+                    displayName: displayName,
+                    formalName: formalNameController.text.trim(),
+                    department: departmentController.text.trim(),
+                    address: addressController.text.trim(),
+                  );
+              Navigator.pop(context);
+              widget.onCustomerSelected(updatedCustomer);
+            },
+            child: const Text("保存して確定"),
+          ),
+        ],
+      ),
+    );
+  }
+
+  /// 削除確認ダイアログ
+  void _confirmDelete(Customer customer) {
+    showDialog(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: const Text("顧客の削除"),
+        content: Text("「${customer.formalName}」をマスターから削除しますか？\n(過去の請求書ファイルは削除されません)"),
+        actions: [
+          TextButton(onPressed: () => Navigator.pop(context), child: const Text("キャンセル")),
+          TextButton(
+            onPressed: () {
+              Navigator.pop(context);
+              if (widget.onCustomerDeleted != null) {
+                widget.onCustomerDeleted!(customer);
+                setState(() {
+                  _filterCustomers(_searchQuery); // リスト更新
+                });
+              }
+            },
+            child: const Text("削除する", style: TextStyle(color: Colors.red)),
+          ),
+        ],
+      ),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Material(
+      child: Column(
+        children: [
+          Padding(
+            padding: const EdgeInsets.all(16.0),
+            child: Column(
+              crossAxisAlignment: CrossAxisAlignment.start,
+              children: [
+                Row(
+                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
+                  children: [
+                    const Text("顧客マスター管理", style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold)),
+                    IconButton(icon: const Icon(Icons.close), onPressed: () => Navigator.pop(context)),
+                  ],
+                ),
+                const SizedBox(height: 12),
+                TextField(
+                  decoration: InputDecoration(
+                    hintText: "登録済み顧客を検索...",
+                    prefixIcon: const Icon(Icons.search),
+                    border: OutlineInputBorder(borderRadius: BorderRadius.circular(8)),
+                  ),
+                  onChanged: _filterCustomers,
+                ),
+                const SizedBox(height: 12),
+                SizedBox(
+                  width: double.infinity,
+                  child: ElevatedButton.icon(
+                    onPressed: _isImportingFromContacts ? null : _importFromPhoneContacts,
+                    icon: _isImportingFromContacts
+                        ? const SizedBox(width: 20, height: 20, child: CircularProgressIndicator(strokeWidth: 2))
+                        : const Icon(Icons.contact_phone),
+                    label: const Text("電話帳から新規取り込み"),
+                    style: ElevatedButton.styleFrom(backgroundColor: Colors.blueGrey.shade700, foregroundColor: Colors.white),
+                  ),
+                ),
+              ],
+            ),
+          ),
+          const Divider(),
+          Expanded(
+            child: _filteredCustomers.isEmpty
+                ? const Center(child: Text("該当する顧客がいません"))
+                : ListView.builder(
+                    itemCount: _filteredCustomers.length,
+                    itemBuilder: (context, index) {
+                      final customer = _filteredCustomers[index];
+                      return ListTile(
+                        leading: const CircleAvatar(child: Icon(Icons.business)),
+                        title: Text(customer.formalName),
+                        subtitle: Text(customer.department?.isNotEmpty == true ? customer.department! : "部署未設定"),
+                        onTap: () => widget.onCustomerSelected(customer),
+                        trailing: Row(
+                          mainAxisSize: MainAxisSize.min,
+                          children: [
+                            IconButton(
+                              icon: const Icon(Icons.edit, color: Colors.blueGrey, size: 20),
+                              onPressed: () => _showCustomerEditDialog(
+                                displayName: customer.displayName,
+                                initialFormalName: customer.formalName,
+                                existingCustomer: customer,
+                              ),
+                            ),
+                            IconButton(
+                              icon: const Icon(Icons.delete_outline, color: Colors.redAccent, size: 20),
+                              onPressed: () => _confirmDelete(customer),
+                            ),
+                          ],
+                        ),
+                      );
+                    },
+                  ),
+          ),
+        ],
+      ),
+    );
+  }
+}
+
+/// 電話帳から一人選ぶための内部ウィジェット
+class _PhoneContactListSelector extends StatefulWidget {
+  final List<Contact> contacts;
+  const _PhoneContactListSelector({required this.contacts});
+
+  @override
+  State<_PhoneContactListSelector> createState() => _PhoneContactListSelectorState();
+}
+
+class _PhoneContactListSelectorState extends State<_PhoneContactListSelector> {
+  List<Contact> _filtered = [];
+  final _searchController = TextEditingController();
+
+  @override
+  void initState() {
+    super.initState();
+    _filtered = widget.contacts;
+  }
+
+  void _onSearch(String q) {
+    setState(() {
+      _filtered = widget.contacts
+          .where((c) => c.displayName.toLowerCase().contains(q.toLowerCase()))
+          .toList();
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return FractionallySizedBox(
+      heightFactor: 0.8,
+      child: Column(
+        children: [
+          Padding(
+            padding: const EdgeInsets.all(16.0),
+            child: TextField(
+              controller: _searchController,
+              decoration: const InputDecoration(hintText: "電話帳から検索...", prefixIcon: Icon(Icons.search)),
+              onChanged: _onSearch,
+            ),
+          ),
+          Expanded(
+            child: ListView.builder(
+              itemCount: _filtered.length,
+              itemBuilder: (context, index) => ListTile(
+                title: Text(_filtered[index].displayName),
+                onTap: () => Navigator.pop(context, _filtered[index]),
+              ),
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}
diff --git a/gemi_invoice/lib/screens/invoice_detail_page.dart b/gemi_invoice/lib/screens/invoice_detail_page.dart
index d475869..8b4f3fc 100644
--- a/gemi_invoice/lib/screens/invoice_detail_page.dart
+++ b/gemi_invoice/lib/screens/invoice_detail_page.dart
@@ -4,7 +4,9 @@ import 'package:intl/intl.dart';
 import 'package:share_plus/share_plus.dart';
 import 'package:open_filex/open_filex.dart';
 import '../models/invoice_models.dart';
+import '../models/customer_model.dart';
 import '../services/pdf_generator.dart';
+import 'product_picker_modal.dart';
 
 class InvoiceDetailPage extends StatefulWidget {
   final Invoice invoice;
@@ -16,7 +18,7 @@ class InvoiceDetailPage extends StatefulWidget {
 }
 
 class _InvoiceDetailPageState extends State<InvoiceDetailPage> {
-  late TextEditingController _clientController;
+  late TextEditingController _formalNameController;
   late TextEditingController _notesController;
   late List<InvoiceItem> _items;
   late bool _isEditing;
@@ -28,7 +30,7 @@ class _InvoiceDetailPageState extends State<InvoiceDetailPage> {
     super.initState();
     _currentInvoice = widget.invoice;
     _currentFilePath = widget.invoice.filePath;
-    _clientController = TextEditingController(text: _currentInvoice.clientName);
+    _formalNameController = TextEditingController(text: _currentInvoice.customer.formalName);
     _notesController = TextEditingController(text: _currentInvoice.notes ?? "");
     _items = List.from(_currentInvoice.items);
     _isEditing = false;
@@ -36,7 +38,7 @@ class _InvoiceDetailPageState extends State<InvoiceDetailPage> {
 
   @override
   void dispose() {
-    _clientController.dispose();
+    _formalNameController.dispose();
     _notesController.dispose();
     super.dispose();
   }
@@ -53,17 +55,41 @@ class _InvoiceDetailPageState extends State<InvoiceDetailPage> {
     });
   }
 
+  void _pickFromMaster() {
+    showModalBottomSheet(
+      context: context,
+      isScrollControlled: true,
+      backgroundColor: Colors.transparent,
+      builder: (context) => FractionallySizedBox(
+        heightFactor: 0.9,
+        child: ProductPickerModal(
+          onItemSelected: (item) {
+            setState(() {
+              _items.add(item);
+            });
+            Navigator.pop(context);
+          },
+        ),
+      ),
+    );
+  }
+
   Future<void> _saveChanges() async {
-    final String clientName = _clientController.text.trim();
-    if (clientName.isEmpty) {
+    final String formalName = _formalNameController.text.trim();
+    if (formalName.isEmpty) {
       ScaffoldMessenger.of(context).showSnackBar(
-        const SnackBar(content: Text('取引先名を入力してください')),
+        const SnackBar(content: Text('取引先の正式名称を入力してください')),
       );
       return;
     }
 
+    // 顧客情報を更新
+    final updatedCustomer = _currentInvoice.customer.copyWith(
+      formalName: formalName,
+    );
+
     final updatedInvoice = _currentInvoice.copyWith(
-      clientName: clientName,
+      customer: updatedCustomer,
       items: _items,
       notes: _notesController.text,
     );
@@ -84,7 +110,6 @@ class _InvoiceDetailPageState extends State<InvoiceDetailPage> {
 
   void _exportCsv() {
     final csvData = _currentInvoice.toCsv();
-    // 実際にはファイル保存ダイアログなどを出すのが望ましいが、ここでは簡易的に共有
     Share.share(csvData, subject: '請求書データ_CSV');
   }
 
@@ -119,10 +144,25 @@ class _InvoiceDetailPageState extends State<InvoiceDetailPage> {
             if (_isEditing)
               Padding(
                 padding: const EdgeInsets.only(top: 8.0),
-                child: ElevatedButton.icon(
-                  onPressed: _addItem,
-                  icon: const Icon(Icons.add),
-                  label: const Text("行を追加"),
+                child: Wrap(
+                  spacing: 12,
+                  runSpacing: 8,
+                  children: [
+                    ElevatedButton.icon(
+                      onPressed: _addItem,
+                      icon: const Icon(Icons.add),
+                      label: const Text("空の行を追加"),
+                    ),
+                    ElevatedButton.icon(
+                      onPressed: _pickFromMaster,
+                      icon: const Icon(Icons.list_alt),
+                      label: const Text("マスターから選択"),
+                      style: ElevatedButton.styleFrom(
+                        backgroundColor: Colors.blueGrey.shade700,
+                        foregroundColor: Colors.white,
+                      ),
+                    ),
+                  ],
                 ),
               ),
             const SizedBox(height: 24),
@@ -136,13 +176,14 @@ class _InvoiceDetailPageState extends State<InvoiceDetailPage> {
   }
 
   Widget _buildHeaderSection() {
+    final dateFormatter = DateFormat('yyyy年MM月dd日');
     return Column(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: [
         if (_isEditing) ...[
           TextField(
-            controller: _clientController,
-            decoration: const InputDecoration(labelText: "取引先名", border: OutlineInputBorder()),
+            controller: _formalNameController,
+            decoration: const InputDecoration(labelText: "取引先 正式名称", border: OutlineInputBorder()),
           ),
           const SizedBox(height: 12),
           TextField(
@@ -151,9 +192,13 @@ class _InvoiceDetailPageState extends State<InvoiceDetailPage> {
             decoration: const InputDecoration(labelText: "備考", border: OutlineInputBorder()),
           ),
         ] else ...[
-          Text("宛名: ${_currentInvoice.clientName} 御中", style: const TextStyle(fontSize: 20, fontWeight: FontWeight.bold)),
+          Text("${_currentInvoice.customer.formalName} ${_currentInvoice.customer.title}",
+              style: const TextStyle(fontSize: 20, fontWeight: FontWeight.bold)),
+          if (_currentInvoice.customer.department != null && _currentInvoice.customer.department!.isNotEmpty)
+            Text(_currentInvoice.customer.department!, style: const TextStyle(fontSize: 16)),
           const SizedBox(height: 4),
           Text("請求番号: ${_currentInvoice.invoiceNumber}"),
+          Text("発行日: ${dateFormatter.format(_currentInvoice.date)}"),
           if (_currentInvoice.notes?.isNotEmpty ?? false) ...[
             const SizedBox(height: 8),
             Text("備考: ${_currentInvoice.notes}", style: const TextStyle(color: Colors.black87)),
diff --git a/gemi_invoice/lib/screens/invoice_input_screen.dart b/gemi_invoice/lib/screens/invoice_input_screen.dart
index 6537722..0259d29 100644
--- a/gemi_invoice/lib/screens/invoice_input_screen.dart
+++ b/gemi_invoice/lib/screens/invoice_input_screen.dart
@@ -1,8 +1,10 @@
-// lib/screens/invoice_input_screen.dart
 import 'package:flutter/material.dart';
-import 'package:flutter_contacts/flutter_contacts.dart';
+import 'package:uuid/uuid.dart';
+import '../models/customer_model.dart';
 import '../models/invoice_models.dart';
 import '../services/pdf_generator.dart';
+import '../services/invoice_repository.dart';
+import 'customer_picker_modal.dart';
 
 /// 請求書の初期入力（ヘッダー部分）を管理するウィジェット
 class InvoiceInputForm extends StatefulWidget {
@@ -18,9 +20,32 @@ class InvoiceInputForm extends StatefulWidget {
 }
 
 class _InvoiceInputFormState extends State<InvoiceInputForm> {
-  final _clientController = TextEditingController(text: "佐々木製作所");
+  final _clientController = TextEditingController();
   final _amountController = TextEditingController(text: "250000");
-  String _status = "取引先と基本金額を入力してPDFを生成してください";
+  final _repository = InvoiceRepository();
+  String _status = "取引先を選択してPDFを生成してください";
+
+  List<Customer> _customerBuffer = [];
+  Customer? _selectedCustomer;
+
+  @override
+  void initState() {
+    super.initState();
+    _selectedCustomer = Customer(
+      id: const Uuid().v4(),
+      displayName: "佐々木製作所",
+      formalName: "株式会社 佐々木製作所",
+    );
+    _customerBuffer.add(_selectedCustomer!);
+    _clientController.text = _selectedCustomer!.formalName;
+
+    // 起動時に不要なPDFを掃除する
+    _repository.cleanupOrphanedPdfs().then((count) {
+      if (count > 0) {
+        debugPrint('Cleaned up $count orphaned PDF files.');
+      }
+    });
+  }
 
   @override
   void dispose() {
@@ -29,64 +54,43 @@ class _InvoiceInputFormState extends State<InvoiceInputForm> {
     super.dispose();
   }
 
-  // 連絡先を選択する処理
-  Future<void> _pickContact() async {
-    setState(() => _status = "連絡先をスキャン中...");
-    try {
-      if (await FlutterContacts.requestPermission(readonly: true)) {
-        final List<Contact> contacts = await FlutterContacts.getContacts(
-          withProperties: false,
-          withThumbnail: false,
-        );
+  Future<void> _openCustomerPicker() async {
+    setState(() => _status = "顧客マスターを開いています...");
 
-        if (!mounted) return;
+    await showModalBottomSheet<void>(
+      context: context,
+      isScrollControlled: true,
+      backgroundColor: Colors.transparent,
+      builder: (context) => FractionallySizedBox(
+        heightFactor: 0.9,
+        child: CustomerPickerModal(
+          existingCustomers: _customerBuffer,
+          onCustomerSelected: (customer) {
+            setState(() {
+              bool exists = _customerBuffer.any((c) => c.id == customer.id);
+              if (!exists) {
+                _customerBuffer.add(customer);
+              }
 
-        if (contacts.isEmpty) {
-          setState(() => _status = "連絡先が空、または取得できませんでした。");
-          return;
-        }
-
-        contacts.sort((a, b) => a.displayName.compareTo(b.displayName));
-
-        final Contact? selected = await showModalBottomSheet<Contact>(
-          context: context,
-          isScrollControlled: true,
-          builder: (BuildContext modalContext) => FractionallySizedBox(
-            heightFactor: 0.8,
-            child: ContactPickerModal(
-              contacts: contacts,
-              onContactSelected: (selectedContact) {
-                Navigator.pop(modalContext, selectedContact);
-              },
-            ),
-          ),
-        );
-
-        if (selected != null) {
-          setState(() {
-            _clientController.text = selected.displayName;
-            _status = "「${selected.displayName}」をセットしました";
-          });
-        }
-      } else {
-        setState(() => _status = "電話帳の権限が拒否されています。");
-      }
-    } catch (e) {
-      setState(() => _status = "エラーが発生しました: $e");
-    }
+              _selectedCustomer = customer;
+              _clientController.text = customer.formalName;
+              _status = "「${customer.formalName}」を選択しました";
+            });
+            Navigator.pop(context);
+          },
+        ),
+      ),
+    );
   }
 
-  // 初期PDFを生成して保存する処理（ここから詳細ページへ遷移する）
   Future<void> _handleInitialGenerate() async {
-    final clientName = _clientController.text.trim();
-    final unitPrice = int.tryParse(_amountController.text) ?? 0;
-
-    if (clientName.isEmpty) {
-      setState(() => _status = "取引先名を入力してください");
+    if (_selectedCustomer == null) {
+      setState(() => _status = "取引先を選択してください");
       return;
     }
 
-    // 初期の1行明細を作成
+    final unitPrice = int.tryParse(_amountController.text) ?? 0;
+
     final initialItems = [
       InvoiceItem(
         description: "ご請求分",
@@ -96,7 +100,7 @@ class _InvoiceInputFormState extends State<InvoiceInputForm> {
     ];
 
     final invoice = Invoice(
-      clientName: clientName,
+      customer: _selectedCustomer!,
       date: DateTime.now(),
       items: initialItems,
     );
@@ -106,8 +110,12 @@ class _InvoiceInputFormState extends State<InvoiceInputForm> {
 
     if (path != null) {
       final updatedInvoice = invoice.copyWith(filePath: path);
+
+      // オリジナルDBに保存
+      await _repository.saveInvoice(updatedInvoice);
+
       widget.onInvoiceGenerated(updatedInvoice, path);
-      setState(() => _status = "PDFを生成しました。詳細ページで表編集が可能です。");
+      setState(() => _status = "PDFを生成しDBに登録しました。");
     } else {
       setState(() => _status = "PDFの生成に失敗しました");
     }
@@ -119,21 +127,30 @@ class _InvoiceInputFormState extends State<InvoiceInputForm> {
       padding: const EdgeInsets.all(16.0),
       child: SingleChildScrollView(
         child: Column(children: [
+          const Text(
+            "ステップ1: 宛先と基本金額の設定",
+            style: TextStyle(fontWeight: FontWeight.bold, color: Colors.blueGrey),
+          ),
+          const SizedBox(height: 16),
           Row(children: [
             Expanded(
               child: TextField(
                 controller: _clientController,
+                readOnly: true,
+                onTap: _openCustomerPicker,
                 decoration: const InputDecoration(
-                  labelText: "取引先名",
-                  hintText: "会社名や個人名",
+                  labelText: "取引先名 (タップして選択)",
+                  hintText: "電話帳から取り込むか、マスターから選択",
+                  prefixIcon: Icon(Icons.business),
                   border: OutlineInputBorder(),
                 ),
               ),
             ),
             const SizedBox(width: 8),
             IconButton(
-              icon: const Icon(Icons.person_search, color: Colors.blue, size: 40),
-              onPressed: _pickContact,
+              icon: const Icon(Icons.person_add_alt_1, color: Colors.indigo, size: 40),
+              onPressed: _openCustomerPicker,
+              tooltip: "顧客を選択・登録",
             ),
           ]),
           const SizedBox(height: 16),
@@ -142,7 +159,8 @@ class _InvoiceInputFormState extends State<InvoiceInputForm> {
             keyboardType: TextInputType.number,
             decoration: const InputDecoration(
               labelText: "基本金額 (税抜)",
-              hintText: "後で詳細ページで変更・追加できます",
+              hintText: "明細の1行目として登録されます",
+              prefixIcon: Icon(Icons.currency_yen),
               border: OutlineInputBorder(),
             ),
           ),
@@ -155,6 +173,8 @@ class _InvoiceInputFormState extends State<InvoiceInputForm> {
               minimumSize: const Size(double.infinity, 60),
               backgroundColor: Colors.indigo,
               foregroundColor: Colors.white,
+              elevation: 4,
+              shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(12)),
             ),
           ),
           const SizedBox(height: 24),
@@ -164,6 +184,7 @@ class _InvoiceInputFormState extends State<InvoiceInputForm> {
             decoration: BoxDecoration(
               color: Colors.grey[100],
               borderRadius: BorderRadius.circular(8),
+              border: Border.all(color: Colors.grey.shade300),
             ),
             child: Text(
               _status,
@@ -176,79 +197,3 @@ class _InvoiceInputFormState extends State<InvoiceInputForm> {
     );
   }
 }
-
-// 連絡先選択用のモーダルウィジェット
-class ContactPickerModal extends StatefulWidget {
-  final List<Contact> contacts;
-  final Function(Contact) onContactSelected;
-
-  const ContactPickerModal({
-    Key? key,
-    required this.contacts,
-    required this.onContactSelected,
-  }) : super(key: key);
-
-  @override
-  State<ContactPickerModal> createState() => _ContactPickerModalState();
-}
-
-class _ContactPickerModalState extends State<ContactPickerModal> {
-  String _searchQuery = "";
-  List<Contact> _filteredContacts = [];
-
-  @override
-  void initState() {
-    super.initState();
-    _filteredContacts = widget.contacts;
-  }
-
-  void _filterContacts(String query) {
-    setState(() {
-      _searchQuery = query.toLowerCase();
-      _filteredContacts = widget.contacts
-          .where((c) => c.displayName.toLowerCase().contains(_searchQuery))
-          .toList();
-    });
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    return Material(
-      child: Column(
-        children: [
-          Padding(
-            padding: const EdgeInsets.all(16.0),
-            child: Column(
-              crossAxisAlignment: CrossAxisAlignment.start,
-              children: [
-                Text(
-                  "取引先を選択 (${_filteredContacts.length}件)",
-                  style: Theme.of(context).textTheme.headlineSmall,
-                ),
-                const SizedBox(height: 12),
-                TextField(
-                  decoration: InputDecoration(
-                    hintText: "名前で検索...",
-                    prefixIcon: const Icon(Icons.search),
-                    border: OutlineInputBorder(borderRadius: BorderRadius.circular(8.0)),
-                  ),
-                  onChanged: _filterContacts,
-                ),
-              ],
-            ),
-          ),
-          Expanded(
-            child: ListView.builder(
-              itemCount: _filteredContacts.length,
-              itemBuilder: (c, i) => ListTile(
-                leading: const CircleAvatar(child: Icon(Icons.person)),
-                title: Text(_filteredContacts[i].displayName),
-                onTap: () => widget.onContactSelected(_filteredContacts[i]),
-              ),
-            ),
-          ),
-        ],
-      ),
-    );
-  }
-}
diff --git a/gemi_invoice/lib/screens/product_picker_modal.dart b/gemi_invoice/lib/screens/product_picker_modal.dart
new file mode 100644
index 0000000..19f4c63
--- /dev/null
+++ b/gemi_invoice/lib/screens/product_picker_modal.dart
@@ -0,0 +1,255 @@
+import 'package:flutter/material.dart';
+import 'package:uuid/uuid.dart';
+import '../data/product_master.dart';
+import '../models/invoice_models.dart';
+
+/// 商品マスターの選択・登録・編集・削除を行うモーダル
+class ProductPickerModal extends StatefulWidget {
+  final Function(InvoiceItem) onItemSelected;
+
+  const ProductPickerModal({
+    Key? key,
+    required this.onItemSelected,
+  }) : super(key: key);
+
+  @override
+  State<ProductPickerModal> createState() => _ProductPickerModalState();
+}
+
+class _ProductPickerModalState extends State<ProductPickerModal> {
+  String _searchQuery = "";
+  List<Product> _masterProducts = [];
+  List<Product> _filteredProducts = [];
+  String _selectedCategory = "すべて";
+
+  @override
+  void initState() {
+    super.initState();
+    // 本来は永続化層から取得するが、現在はProductMasterの初期データを使用
+    _masterProducts = List.from(ProductMaster.products);
+    _filterProducts();
+  }
+
+  void _filterProducts() {
+    setState(() {
+      _filteredProducts = _masterProducts.where((product) {
+        final matchesQuery = product.name.toLowerCase().contains(_searchQuery.toLowerCase()) ||
+            product.id.toLowerCase().contains(_searchQuery.toLowerCase());
+        final matchesCategory = _selectedCategory == "すべて" || (product.category == _selectedCategory);
+        return matchesQuery && matchesCategory;
+      }).toList();
+    });
+  }
+
+  /// 商品の編集・新規登録用ダイアログ
+  void _showProductEditDialog({Product? existingProduct}) {
+    final idController = TextEditingController(text: existingProduct?.id ?? "");
+    final nameController = TextEditingController(text: existingProduct?.name ?? "");
+    final priceController = TextEditingController(text: existingProduct?.defaultUnitPrice.toString() ?? "");
+    final categoryController = TextEditingController(text: existingProduct?.category ?? "");
+
+    showDialog(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: Text(existingProduct == null ? "新規商品の登録" : "商品情報の編集"),
+        content: SingleChildScrollView(
+          child: Column(
+            mainAxisSize: MainAxisSize.min,
+            children: [
+              if (existingProduct == null)
+                TextField(
+                  controller: idController,
+                  decoration: const InputDecoration(labelText: "商品コード (例: S001)", border: OutlineInputBorder()),
+                ),
+              const SizedBox(height: 12),
+              TextField(
+                controller: nameController,
+                decoration: const InputDecoration(labelText: "商品名", border: OutlineInputBorder()),
+              ),
+              const SizedBox(height: 12),
+              TextField(
+                controller: priceController,
+                keyboardType: TextInputType.number,
+                decoration: const InputDecoration(labelText: "標準単価", border: OutlineInputBorder()),
+              ),
+              const SizedBox(height: 12),
+              TextField(
+                controller: categoryController,
+                decoration: const InputDecoration(labelText: "カテゴリ (任意)", border: OutlineInputBorder()),
+              ),
+            ],
+          ),
+        ),
+        actions: [
+          TextButton(onPressed: () => Navigator.pop(context), child: const Text("キャンセル")),
+          ElevatedButton(
+            onPressed: () {
+              final String name = nameController.text.trim();
+              final int price = int.tryParse(priceController.text) ?? 0;
+              if (name.isEmpty) return;
+
+              setState(() {
+                if (existingProduct != null) {
+                  // 更新
+                  final index = _masterProducts.indexWhere((p) => p.id == existingProduct.id);
+                  if (index != -1) {
+                    _masterProducts[index] = existingProduct.copyWith(
+                      name: name,
+                      defaultUnitPrice: price,
+                      category: categoryController.text.trim(),
+                    );
+                  }
+                } else {
+                  // 新規追加
+                  _masterProducts.add(Product(
+                    id: idController.text.isEmpty ? const Uuid().v4().substring(0, 8) : idController.text,
+                    name: name,
+                    defaultUnitPrice: price,
+                    category: categoryController.text.trim(),
+                  ));
+                }
+                _filterProducts();
+              });
+              Navigator.pop(context);
+            },
+            child: const Text("保存"),
+          ),
+        ],
+      ),
+    );
+  }
+
+  /// 削除確認
+  void _confirmDelete(Product product) {
+    showDialog(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: const Text("商品の削除"),
+        content: Text("「${product.name}」をマスターから削除しますか？"),
+        actions: [
+          TextButton(onPressed: () => Navigator.pop(context), child: const Text("キャンセル")),
+          TextButton(
+            onPressed: () {
+              setState(() {
+                _masterProducts.removeWhere((p) => p.id == product.id);
+                _filterProducts();
+              });
+              Navigator.pop(context);
+            },
+            child: const Text("削除する", style: TextStyle(color: Colors.red)),
+          ),
+        ],
+      ),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    // マスター内のカテゴリを動的に取得
+    final dynamicCategories = ["すべて", ..._masterProducts.map((p) => p.category ?? 'その他').toSet().toList()];
+
+    return Material(
+      color: Colors.white,
+      child: Column(
+        children: [
+          Padding(
+            padding: const EdgeInsets.all(16.0),
+            child: Column(
+              crossAxisAlignment: CrossAxisAlignment.start,
+              children: [
+                Row(
+                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
+                  children: [
+                    const Text("商品マスター管理", style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold)),
+                    IconButton(icon: const Icon(Icons.close), onPressed: () => Navigator.pop(context)),
+                  ],
+                ),
+                const SizedBox(height: 12),
+                TextField(
+                  decoration: InputDecoration(
+                    hintText: "商品名やコードで検索...",
+                    prefixIcon: const Icon(Icons.search),
+                    border: OutlineInputBorder(borderRadius: BorderRadius.circular(12)),
+                    filled: true,
+                    fillColor: Colors.grey.shade50,
+                  ),
+                  onChanged: (val) {
+                    _searchQuery = val;
+                    _filterProducts();
+                  },
+                ),
+                const SizedBox(height: 12),
+                Row(
+                  children: [
+                    Expanded(
+                      child: SingleChildScrollView(
+                        scrollDirection: Axis.horizontal,
+                        child: Row(
+                          children: dynamicCategories.map((cat) {
+                            final isSelected = _selectedCategory == cat;
+                            return Padding(
+                              padding: const EdgeInsets.only(right: 8.0),
+                              child: ChoiceChip(
+                                label: Text(cat),
+                                selected: isSelected,
+                                onSelected: (s) {
+                                  if (s) {
+                                    setState(() {
+                                      _selectedCategory = cat;
+                                      _filterProducts();
+                                    });
+                                  }
+                                },
+                              ),
+                            );
+                          }).toList(),
+                        ),
+                      ),
+                    ),
+                    const SizedBox(width: 8),
+                    IconButton.filled(
+                      onPressed: () => _showProductEditDialog(),
+                      icon: const Icon(Icons.add),
+                      tooltip: "新規商品を追加",
+                    ),
+                  ],
+                ),
+              ],
+            ),
+          ),
+          const Divider(height: 1),
+          Expanded(
+            child: _filteredProducts.isEmpty
+                ? const Center(child: Text("該当する商品がありません"))
+                : ListView.separated(
+                    itemCount: _filteredProducts.length,
+                    separatorBuilder: (context, index) => const Divider(height: 1),
+                    itemBuilder: (context, index) {
+                      final product = _filteredProducts[index];
+                      return ListTile(
+                        leading: const Icon(Icons.inventory_2, color: Colors.blueGrey),
+                        title: Text(product.name, style: const TextStyle(fontWeight: FontWeight.bold)),
+                        subtitle: Text("${product.id} | ¥${product.defaultUnitPrice}"),
+                        onTap: () => widget.onItemSelected(product.toInvoiceItem()),
+                        trailing: Row(
+                          mainAxisSize: MainAxisSize.min,
+                          children: [
+                            IconButton(
+                              icon: const Icon(Icons.edit_outlined, size: 20, color: Colors.blueGrey),
+                              onPressed: () => _showProductEditDialog(existingProduct: product),
+                            ),
+                            IconButton(
+                              icon: const Icon(Icons.delete_outline, size: 20, color: Colors.redAccent),
+                              onPressed: () => _confirmDelete(product),
+                            ),
+                          ],
+                        ),
+                      );
+                    },
+                  ),
+          ),
+        ],
+      ),
+    );
+  }
+}
diff --git a/gemi_invoice/lib/services/invoice_repository.dart b/gemi_invoice/lib/services/invoice_repository.dart
new file mode 100644
index 0000000..46b6c07
--- /dev/null
+++ b/gemi_invoice/lib/services/invoice_repository.dart
@@ -0,0 +1,107 @@
+import 'dart:convert';
+import 'dart:io';
+import 'package:path_provider/path_provider.dart';
+import '../models/invoice_models.dart';
+
+/// 請求書のオリジナルデータを管理するリポジトリ（簡易DB）
+/// PDFファイルとデータの整合性を保つための機能を提供します
+class InvoiceRepository {
+  static const String _dbFileName = 'invoices_db.json';
+
+  /// データベースファイルのパスを取得
+  Future<File> _getDbFile() async {
+    final directory = await getApplicationDocumentsDirectory();
+    return File('${directory.path}/$_dbFileName');
+  }
+
+  /// 全ての請求書データを読み込む
+  Future<List<Invoice>> getAllInvoices() async {
+    try {
+      final file = await _getDbFile();
+      if (!await file.exists()) return [];
+
+      final String content = await file.readAsString();
+      final List<dynamic> jsonList = json.decode(content);
+
+      return jsonList.map((json) => Invoice.fromJson(json)).toList()
+        ..sort((a, b) => b.date.compareTo(a.date)); // 新しい順にソート
+    } catch (e) {
+      print('DB Loading Error: $e');
+      return [];
+    }
+  }
+
+  /// 請求書データを保存・更新する
+  Future<void> saveInvoice(Invoice invoice) async {
+    final List<Invoice> all = await getAllInvoices();
+
+    // 同じ請求番号があれば差し替え、なければ追加
+    final index = all.indexWhere((i) => i.invoiceNumber == invoice.invoiceNumber);
+    if (index != -1) {
+      // 古いファイルが存在し、かつ新しいパスと異なる場合は古いファイルを削除（無駄なPDFの掃除）
+      final oldPath = all[index].filePath;
+      if (oldPath != null && oldPath != invoice.filePath) {
+        await _deletePhysicalFile(oldPath);
+      }
+      all[index] = invoice;
+    } else {
+      all.add(invoice);
+    }
+
+    final file = await _getDbFile();
+    await file.writeAsString(json.encode(all.map((i) => i.toJson()).toList()));
+  }
+
+  /// 請求書データを削除する
+  Future<void> deleteInvoice(Invoice invoice) async {
+    final List<Invoice> all = await getAllInvoices();
+    all.removeWhere((i) => i.invoiceNumber == invoice.invoiceNumber);
+
+    // 物理ファイルも削除
+    if (invoice.filePath != null) {
+      await _deletePhysicalFile(invoice.filePath!);
+    }
+
+    final file = await _getDbFile();
+    await file.writeAsString(json.encode(all.map((i) => i.toJson()).toList()));
+  }
+
+  /// 実際のPDFファイルをストレージから削除する
+  Future<void> _deletePhysicalFile(String path) async {
+    try {
+      final file = File(path);
+      if (await file.exists()) {
+        await file.delete();
+        print('Physical file deleted: $path');
+      }
+    } catch (e) {
+      print('File Deletion Error: $path, $e');
+    }
+  }
+
+  /// DBに登録されていない「浮いたPDFファイル」をスキャンして掃除する
+  Future<int> cleanupOrphanedPdfs() async {
+    final List<Invoice> all = await getAllInvoices();
+    final Set<String> registeredPaths = all
+        .where((i) => i.filePath != null)
+        .map((i) => i.filePath!)
+        .toSet();
+
+    final directory = await getExternalStorageDirectory();
+    if (directory == null) return 0;
+
+    int deletedCount = 0;
+    final List<FileSystemEntity> files = directory.listSync();
+
+    for (var entity in files) {
+      if (entity is File && entity.path.endsWith('.pdf')) {
+        // DBに登録されていないPDFは削除（無駄なゴミ）
+        if (!registeredPaths.contains(entity.path)) {
+          await entity.delete();
+          deletedCount++;
+        }
+      }
+    }
+    return deletedCount;
+  }
+}
diff --git a/gemi_invoice/lib/services/pdf_generator.dart b/gemi_invoice/lib/services/pdf_generator.dart
index 9fdd670..78d059a 100644
--- a/gemi_invoice/lib/services/pdf_generator.dart
+++ b/gemi_invoice/lib/services/pdf_generator.dart
@@ -59,7 +59,7 @@ Future<String?> generateInvoicePdf(Invoice invoice) async {
                       decoration: const pw.BoxDecoration(
                         border: pw.Border(bottom: pw.BorderSide(width: 1)),
                       ),
-                      child: pw.Text("${invoice.clientName} 御中",
+                      child: pw.Text(invoice.customer.invoiceName,
                         style: const pw.TextStyle(fontSize: 18)),
                     ),
                     pw.SizedBox(height: 10),
@@ -169,7 +169,7 @@ Future<String?> generateInvoicePdf(Invoice invoice) async {
     final Uint8List bytes = await pdf.save();
     final String hash = sha256.convert(bytes).toString().substring(0, 8);
     final String dateFileStr = DateFormat('yyyyMMdd').format(invoice.date);
-    String fileName = "Invoice_${dateFileStr}_${invoice.clientName}_$hash.pdf";
+    String fileName = "Invoice_${dateFileStr}_${invoice.customer.formalName}_$hash.pdf";
 
     final directory = await getExternalStorageDirectory();
     if (directory == null) return null;