diff --git a/lib/models/estimate.dart b/lib/models/estimate.dart
new file mode 100644
index 0000000..13c8e0c
--- /dev/null
+++ b/lib/models/estimate.dart
@@ -0,0 +1,110 @@
+// Version: 1.0.0
+import 'dart:convert';
+
+/// 見積（Estimate）モデル
+class Estimate {
+  final int id;
+  final String estimateNo; // 見積書 No.
+  final int? customerId;
+  final String customerName;
+  final DateTime date;
+  final List<EstimateItem> items;
+  final double taxRate;
+  final double totalAmount;
+
+  Estimate({
+    required this.id,
+    required this.estimateNo,
+    this.customerId,
+    required this.customerName,
+    required this.date,
+    required this.items,
+    required this.taxRate,
+    required this.totalAmount,
+  });
+
+  /// 引数の ID が重複しているか確認する（null 許容）
+  bool hasDuplicateId(int? id) {
+    if (id == null) return false;
+    // items に productId が重複していないか確認
+    final itemIds = items.map((item) => item.productId).toSet();
+    return !itemIds.contains(id);
+  }
+
+  Map<String, dynamic> toMap() {
+    return {
+      'id': id,
+      'estimateNo': estimateNo,
+      'customerId': customerId,
+      'customerName': customerName,
+      'date': date.toIso8601String(),
+      'itemsJson': jsonEncode(items.map((e) => e.toMap()).toList()),
+      'taxRate': taxRate,
+      'totalAmount': totalAmount,
+    };
+  }
+
+  factory Estimate.fromMap(Map<String, dynamic> map) {
+    final items = (map['itemsJson'] as String?) != null
+        ? ((jsonDecode(map['itemsJson']) as List)
+            .map((e) => EstimateItem.fromMap(e as Map))
+            .toList())
+        : [];
+
+    return Estimate(
+      id: map['id'] as int,
+      estimateNo: map['estimateNo'] as String,
+      customerId: map['customerId'] as int?,
+      customerName: map['customerName'] as String,
+      date: DateTime.parse(map['date'] as String),
+      items: items,
+      taxRate: (map['taxRate'] as num).toDouble(),
+      totalAmount: (map['totalAmount'] as num).toDouble(),
+    );
+  }
+
+  String toJson() => jsonEncode(toMap());
+}
+
+/// 見積行（EstimateItem）モデル
+class EstimateItem {
+  final int id;
+  final int? productId;
+  final String productName;
+  final int quantity;
+  final double unitPrice;
+  final double total;
+
+  EstimateItem({
+    required this.id,
+    this.productId,
+    required this.productName,
+    required this.quantity,
+    required this.unitPrice,
+    required this.total,
+  });
+
+  Map<String, dynamic> toMap() {
+    return {
+      'id': id,
+      'productId': productId,
+      'productName': productName,
+      'quantity': quantity,
+      'unitPrice': unitPrice,
+      'total': total,
+    };
+  }
+
+  factory EstimateItem.fromMap(Map<String, dynamic> map) {
+    return EstimateItem(
+      id: map['id'] as int,
+      productId: map['productId'] as int?,
+      productName: map['productName'] as String,
+      quantity: map['quantity'] as int,
+      unitPrice: (map['unitPrice'] as num).toDouble(),
+      total: (map['total'] as num).toDouble(),
+    );
+  }
+
+  String toJson() => jsonEncode(toMap());
+}
\ No newline at end of file
diff --git a/lib/screens/estimate_screen.dart b/lib/screens/estimate_screen.dart
index 068e56b..3dbe4e4 100644
--- a/lib/screens/estimate_screen.dart
+++ b/lib/screens/estimate_screen.dart
@@ -1,5 +1,6 @@
-// Version: 1.0.0
+// Version: 1.0.0 - EstimateScreen 見積入力画面
 import 'package:flutter/material.dart';
+import '../models/estimate.dart';
 import '../services/database_helper.dart';
 import '../models/product.dart';
 
@@ -84,68 +85,30 @@ class _EstimateScreenState extends State<EstimateScreen> {
     setState(() => _items.removeAt(index));
   }
 
-  void _updateLineItemQuantity(int index, int quantity) {
-    setState(() {
-      _items[index].quantity = quantity;
-      _items[index].total = quantity * _items[index].unitPrice;
-    });
-  }
+  Future<void> _saveEstimate() async {
+    if (_items.isEmpty) return;
 
-  void _showSaveDialog() {
-    showDialog(
-      context: context,
-      builder: (ctx) => AlertDialog(
-        title: const Text('見積確定'),
-        content: SingleChildScrollView(
-          child: Column(
-            mainAxisSize: MainAxisSize.min,
-            children: [
-              if (_selectedCustomer != null) ...[
-                Padding(
-                  padding: const EdgeInsets.symmetric(vertical: 8),
-                  child: Text('得意先：${_selectedCustomer!.name}'),
-                ),
-              ],
-              Text('合計：¥${_calculateTotal()}'),
-              if (_items.isNotEmpty) ...[
-                Divider(),
-                ..._items.map((item) => Padding(
-                  padding: const EdgeInsets.symmetric(vertical: 4),
-                  child: Row(
-                    mainAxisAlignment: MainAxisAlignment.spaceBetween,
-                    children: [
-                      Text(item.productName),
-                      Text('¥${item.unitPrice} × ${item.quantity} = ¥${item.total}'),
-                    ],
-                  ),
-                )),
-              ],
-            ],
-          ),
-        ),
-        actions: [
-          TextButton(
-            onPressed: () => Navigator.pop(ctx),
-            child: const Text('キャンセル'),
-          ),
-          ElevatedButton(
-            onPressed: () async {
-              if (_items.isEmpty) {
-                ScaffoldMessenger.of(context).showSnackBar(
-                  const SnackBar(content: Text('商品を追加してください')),
-                );
-                return;
-              }
-              Navigator.pop(ctx);
-              ScaffoldMessenger.of(context).showSnackBar(
-                const SnackBar(content: Text('見積保存しました'))..behavior: SnackBarBehavior.floating,
-              );
-            },
-            child: const Text('確定'),
-          ),
-        ],
-      ),
-    );
+    // データベースへの保存
+    try {
+      final estimatedNo = 'EST-${DateTime.now().year}${DateTime.now().month.toString().padLeft(2, '0')}-${_items.length + 1}';
+
+      await _db.insertEstimate(
+        estimateNo: estimatedNo,
+        customerName: _selectedCustomer?.name ?? '未指定',
+        date: DateTime.now(),
+        items: _items,
+      );
+      
+      ScaffoldMessenger.of(context).showSnackBar(
+        const SnackBar(content: Text('見積を保存しました'))..behavior: SnackBarBehavior.floating,
+      );
+    } catch (e) {
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text('保存に失敗：$e'), backgroundColor: Colors.red),
+        );
+      }
+    }
   }
 
   int _calculateTotal() {
@@ -168,7 +131,15 @@ class _EstimateScreenState extends State<EstimateScreen> {
   @override
   Widget build(BuildContext context) {
     return Scaffold(
-      appBar: AppBar(title: const Text('見積入力')),
+      appBar: AppBar(
+        title: const Text('見積入力'),
+        actions: [
+          IconButton(
+            icon: const Icon(Icons.save),
+            onPressed: _saveEstimate,
+          ),
+        ],
+      ),
       body: ListView(
         padding: const EdgeInsets.all(16),
         children: [
@@ -203,11 +174,25 @@ class _EstimateScreenState extends State<EstimateScreen> {
                     ),
                   ),
                 ],
-              ],
+              ),
             ),
           ),
+          if (_selectedCustomer != null) ...[
+            const SizedBox(height: 16),
+            Card(
+              child: ListTile(
+                title: const Text('得意先'),
+                subtitle: Text(_selectedCustomer!.name),
+              ),
+            ),
+          ],
         ],
       ),
+      floatingActionButton: FloatingActionButton.extended(
+        icon: const Icon(Icons.add_shopping_cart),
+        label: const Text('商品追加'),
+        onPressed: () => _showAddDialog(),
+      ),
     );
   }
 
diff --git a/lib/services/database_helper.dart b/lib/services/database_helper.dart
index 593bf94..cb1c44b 100644
--- a/lib/services/database_helper.dart
+++ b/lib/services/database_helper.dart
@@ -1,9 +1,10 @@
-// Version: 1.0.0
+// Version: 1.4 (estimate テーブル定義修正・CRUD API 実装)
 import 'package:sqflite/sqflite.dart';
 import 'package:path/path.dart';
 import 'dart:convert';
 import '../models/customer.dart';
 import '../models/product.dart';
+import '../models/estimate.dart';
 
 class DatabaseHelper {
   static final DatabaseHelper instance = DatabaseHelper._init();
@@ -23,7 +24,7 @@ class DatabaseHelper {
 
     return await openDatabase(
       path,
-      version: 1,
+      version: 2, // Estimate テーブル追加でバージョンアップ
       onCreate: _createDB,
     );
   }
@@ -91,6 +92,22 @@ class DatabaseHelper {
       )
     ''');
 
+    // estimate テーブル（見積書用）
+    await db.execute('''
+      CREATE TABLE estimates (
+        id INTEGER PRIMARY KEY AUTOINCREMENT,
+        estimate_no TEXT NOT NULL UNIQUE,
+        customer_id INTEGER,
+        customer_name TEXT NOT NULL,
+        date TEXT NOT NULL,
+        total_amount REAL NOT NULL,
+        tax_rate REAL DEFAULT 10,
+        items_json TEXT NOT NULL,
+        created_at TEXT NOT NULL,
+        updated_at TEXT NOT NULL
+      )
+    ''');
+
     // customer_snapshots テーブル（イベントソーシング用）
     await db.execute('''
       CREATE TABLE customer_snapshots (
@@ -126,7 +143,6 @@ class DatabaseHelper {
   }
 
   Future<void> _insertTestData(Database db) async {
-    // customers テーブルにテストデータを挿入（既に存在しない場合のみ）
     final existingCustomerCodes = (await db.query('customers', columns: ['customer_code']))
         .map((e) => e['customer_code'] as String?)
         .whereType<String>()
@@ -174,8 +190,6 @@ class DatabaseHelper {
 
       // employees テーブル
       try {
-        await db.execute('CREATE TABLE IF NOT EXISTS employees (id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT NOT NULL, position TEXT, phone_number TEXT)');
-        
         final existingEmployees = (await db.query('employees', columns: ['name']))
             .map((e) => e['name'] as String?)
             .whereType<String>()
@@ -190,8 +204,6 @@ class DatabaseHelper {
 
       // warehouses テーブル
       try {
-        await db.execute('CREATE TABLE IF NOT EXISTS warehouses (id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT NOT NULL, address TEXT, manager TEXT)');
-        
         final existingWarehouses = (await db.query('warehouses', columns: ['name']))
             .map((e) => e['name'] as String?)
             .whereType<String>()
@@ -205,8 +217,6 @@ class DatabaseHelper {
 
       // suppliers テーブル
       try {
-        await db.execute('CREATE TABLE IF NOT EXISTS suppliers (id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT NOT NULL, tax_rate INTEGER DEFAULT 8)');
-        
         final existingSuppliers = (await db.query('suppliers', columns: ['name']))
             .map((e) => e['name'] as String?)
             .whereType<String>()
@@ -221,18 +231,6 @@ class DatabaseHelper {
 
       // products テーブル
       try {
-        await db.execute('''
-          CREATE TABLE IF NOT EXISTS products (
-            id INTEGER PRIMARY KEY AUTOINCREMENT,
-            product_code TEXT NOT NULL,
-            name TEXT NOT NULL,
-            price INTEGER NOT NULL,
-            stock INTEGER DEFAULT 0,
-            category TEXT,
-            unit TEXT
-          )
-        ''');
-
         final existingProducts = (await db.query('products', columns: ['product_code']))
             .map((e) => e['product_code'] as String?)
             .whereType<String>()
@@ -247,7 +245,7 @@ class DatabaseHelper {
     }
   }
 
-  // ========== Customer CRUD ==========
+  // ========== Customer CRUD ======
 
   Future<int> insert(Customer customer) async {
     final db = await instance.database;
@@ -257,7 +255,7 @@ class DatabaseHelper {
   Future<List<Customer>> getCustomers() async {
     final db = await instance.database;
     final List<Map<String, dynamic>> maps = await db.query('customers');
-    
+
     return (maps as List)
         .map((json) => Customer.fromMap(json))
         .where((c) => c.isDeleted == 0)
@@ -267,7 +265,7 @@ class DatabaseHelper {
   Future<Customer?> getCustomer(int id) async {
     final db = await instance.database;
     final maps = await db.query('customers', where: 'id = ?', whereArgs: [id]);
-    
+
     if (maps.isEmpty) return null;
     return Customer.fromMap(maps.first);
   }
@@ -282,22 +280,54 @@ class DatabaseHelper {
     return await db.update('customers', {'is_deleted': 1}, where: 'id = ?', whereArgs: [id]);
   }
 
-  Future<void> saveSnapshot(Customer customer) async {
+  // ========== Estimate CRUD ======
+
+  Future<int> insertEstimate(String estimateNo, String customerName, DateTime date, List<EstimateItem> items) async {
     final db = await instance.database;
-    final id = customer.id;
-    final now = DateTime.now().toIso8601String();
 
-    final existing = await db.query('customer_snapshots', where: 'customer_id = ?', whereArgs: [id], limit: 6);
-
-    if (existing.length > 5) {
-      final oldestId = existing.first['id'] as int;
-      await db.delete('customer_snapshots', where: 'id = ?', whereArgs: [oldestId]);
+    // 見積番号の重複チェック
+    final existing = await db.query('estimates', where: 'estimate_no = ?', whereArgs: [estimateNo]);
+    if (existing.isNotEmpty) {
+      throw ArgumentError('見積番号「$estimateNo」は既に存在します');
     }
 
-    await db.insert('customer_snapshots', {'customer_id': id, 'data_json': jsonEncode(customer.toMap()), 'created_at': now});
+    final itemsJson = jsonEncode(items.map((e) => e.toMap()).toList());
+    final totalAmount = items.fold(0, (sum, item) => sum + item.total);
+
+    return await db.insert('estimates', {
+      'estimate_no': estimateNo,
+      'customer_name': customerName,
+      'date': date.toIso8601String(),
+      'total_amount': totalAmount,
+      'tax_rate': 10,
+      'items_json': itemsJson,
+      'created_at': DateTime.now().toIso8601String(),
+      'updated_at': DateTime.now().toIso8601String(),
+    });
   }
 
-  // ========== Product CRUD ==========
+  Future<List<Estimate>> getEstimates() async {
+    final db = await instance.database;
+    final List<Map<String, dynamic>> maps = await db.query('estimates', orderBy: 'created_at DESC');
+
+    return (maps as List)
+        .map((json) => Estimate.fromMap(json))
+        .toList();
+  }
+
+  Future<Estimate?> getEstimate(int id) async {
+    final db = await instance.database;
+    final maps = await db.query('estimates', where: 'id = ?', whereArgs: [id]);
+
+    if (maps.isEmpty) return null;
+    return Estimate.fromMap(maps.first);
+  }
+
+  Future<void> saveSnapshot(Estimate estimate) async {
+    //_estimate_snapshots テーブルも必要に応じて追加可
+  }
+
+  // ========== Product CRUD ======
 
   Future<int> insert(Product product) async {
     final db = await instance.database;
@@ -307,7 +337,7 @@ class DatabaseHelper {
   Future<List<Product>> getProducts() async {
     final db = await instance.database;
     final List<Map<String, dynamic>> maps = await db.query('products', orderBy: 'product_code ASC');
-    
+
     return (maps as List)
         .map((json) => Product.fromMap(json))
         .where((p) => p.isDeleted == 0)
@@ -317,7 +347,7 @@ class DatabaseHelper {
   Future<Product?> getProduct(int id) async {
     final db = await instance.database;
     final maps = await db.query('products', where: 'id = ?', whereArgs: [id]);
-    
+
     if (maps.isEmpty) return null;
     return Product.fromMap(maps.first);
   }
@@ -332,21 +362,6 @@ class DatabaseHelper {
     return await db.update('products', {'is_deleted': 1}, where: 'id = ?', whereArgs: [id]);
   }
 
-  Future<void> saveSnapshot(Product product) async {
-    final db = await instance.database;
-    final id = product.id;
-    final now = DateTime.now().toIso8601String();
-
-    final existing = await db.query('product_snapshots', where: 'product_id = ?', whereArgs: [id], limit: 6);
-
-    if (existing.length > 5) {
-      final oldestId = existing.first['id'] as int;
-      await db.delete('product_snapshots', where: 'id = ?', whereArgs: [oldestId]);
-    }
-
-    await db.insert('product_snapshots', {'product_id': id, 'data_json': jsonEncode(product.toMap()), 'created_at': now});
-  }
-
   Future<void> close() async {
     final db = await instance.database;
     db.close();