diff --git a/backend/src/main/java/com/example/todoapp/controller/StocksController.java b/backend/src/main/java/com/example/todoapp/controller/StocksController.java
index cdced2e..78219de 100644
--- a/backend/src/main/java/com/example/todoapp/controller/StocksController.java
+++ b/backend/src/main/java/com/example/todoapp/controller/StocksController.java
@@ -1,5 +1,6 @@
 package com.example.todoapp.controller;
 
+import com.example.todoapp.dto.AddStocksDTO;
 import com.example.todoapp.dto.DeleteStockRequest;
 import com.example.todoapp.dto.ResponseStockDTO;
 import com.example.todoapp.dto.StockDTO;
@@ -75,7 +76,7 @@ public class StocksController {
     @PostMapping("/add")
     public ResponseEntity<StockDTO> createStock(
             Authentication authentication,
-            @Valid @RequestBody Stocks stock) {
+            @Valid @RequestBody AddStocksDTO stock) {
         Stocks createdStock = stockService.createStock(authentication.getName(), stock);
         return ResponseEntity.ok(StockDTO.fromEntity(createdStock));
     }
diff --git a/backend/src/main/java/com/example/todoapp/dto/AddStocksDTO.java b/backend/src/main/java/com/example/todoapp/dto/AddStocksDTO.java
new file mode 100644
index 0000000..84dc6dc
--- /dev/null
+++ b/backend/src/main/java/com/example/todoapp/dto/AddStocksDTO.java
@@ -0,0 +1,57 @@
+//--------------------------------
+// AddStocksDTO.java
+//
+//
+// 更新履歴：2025/06/12 新規作成 
+// Copyright(c) 2025 IVIS All rights reserved.
+//--------------------------------------------
+package com.example.todoapp.dto;
+
+import com.example.todoapp.model.Stocks;
+import lombok.Data;
+import java.time.LocalDate;
+
+/**
+ * 在庫のデータ転送オブジェクト（DTO）
+ * <p>
+ * このクラスはクライアントとサーバー間で在庫情報をやり取りするために使用されます。
+ * エンティティとは異なり、必要な情報のみを含み、関連エンティティへの参照ではなくIDのみを保持します。
+ * </p>
+ */
+
+@Data
+public class AddStocksDTO {
+    private Long stockId;
+    private Long stuffId;
+    private Long userId;
+    private String stuffName;
+    private String category;
+    private String summary;
+    private int amount;
+    private int price;
+    private LocalDate buyDate;
+    private LocalDate lastUpdate;
+    private LocalDate expDate;
+
+    /**
+     * 在庫エンティティからDTOを作成する
+     *
+     * @param stock 変換元の在庫エンティティ
+     * @return 変換されたAddStocksDTOオブジェクト
+     */
+    public static AddStocksDTO fromEntity(Stocks stock) {
+        AddStocksDTO dto = new AddStocksDTO();
+        dto.setStockId(stock.getStockId());
+        dto.setStuffId(stock.getStuff().getStuffId());
+        dto.setUserId(stock.getUser().getId());
+        dto.setStuffName(stock.getStuff().getStuffName());
+        dto.setCategory(stock.getStuff().getCategory());
+        dto.setSummary(stock.getStuff().getSummary());
+        dto.setAmount(stock.getAmount());
+        dto.setPrice(stock.getPrice());
+        dto.setBuyDate(stock.getBuyDate());
+        dto.setLastUpdate(stock.getLastUpdate());
+        dto.setExpDate(stock.getExpDate());
+        return dto;
+    }
+}
\ No newline at end of file
diff --git a/backend/src/main/java/com/example/todoapp/service/StocksService.java b/backend/src/main/java/com/example/todoapp/service/StocksService.java
index 20a3386..adc00b0 100644
--- a/backend/src/main/java/com/example/todoapp/service/StocksService.java
+++ b/backend/src/main/java/com/example/todoapp/service/StocksService.java
@@ -1,16 +1,21 @@
 package com.example.todoapp.service;
 
+import com.example.todoapp.dto.StockDTO;
+import com.example.todoapp.dto.AddStocksDTO;
 import com.example.todoapp.dto.UpdateStockRequest;
 import com.example.todoapp.model.Stocks;
+import com.example.todoapp.model.Stuffs;
 import com.example.todoapp.util.MessageUtils;
 import com.example.todoapp.model.User;
 import com.example.todoapp.repository.StocksRepository;
+import com.example.todoapp.repository.StuffsRepository;
 import com.example.todoapp.repository.UserRepository;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.security.core.userdetails.UsernameNotFoundException;
 import org.springframework.stereotype.Service;
 
 import java.util.List;
+import java.util.Optional;
 
 /**
  * Stocksテーブルのサービスクラス
@@ -23,6 +28,9 @@ public class StocksService {
     @Autowired
     private StocksRepository stocksRepository;
 
+    @Autowired
+    private StuffsRepository stuffsRepository;
+
     @Autowired
     private UserRepository userRepository;
 
@@ -36,10 +44,35 @@ public class StocksService {
      * @param stock 追加する在庫情報
      * @return 保存された在庫エンティティ
      */
-    public Stocks createStock(String username, Stocks stock) {
+    public Stocks createStock(String username, AddStocksDTO stock) {
         User user = getUserByUsername(username);
-        stock.setUser(user);
-        return stocksRepository.save(stock);
+        Stocks stockEntity = new Stocks();
+        Stuffs stuffs;
+        if (stock.getStuffId() == null) {
+            // 新しい材料を作成
+            Stuffs newStuff = new Stuffs();
+            newStuff.setStuffName(stock.getStuffName());
+            newStuff.setSummary(stock.getSummary());
+            newStuff.setCategory(stock.getCategory());
+            stuffs = stuffsRepository.save(newStuff);
+        } else {
+            // 材料情報を取得
+            Optional<Stuffs> existstuffs = stuffsRepository.findById(stock.getStuffId());
+            if (existstuffs == null) {
+                throw new RuntimeException("材料がありません");
+            }
+            stuffs = existstuffs.get();
+        }
+
+        stockEntity.setStockId(stock.getStockId());
+        stockEntity.setStuff(stuffs);
+        stockEntity.setUser(user);
+        stockEntity.setAmount(stock.getAmount());
+        stockEntity.setPrice(stock.getPrice());
+        stockEntity.setBuyDate(stock.getBuyDate());
+        // stockEntity.setLastUpdate(stock.getLastUpdate());
+        stockEntity.setExpDate(stock.getExpDate());
+        return stocksRepository.save(stockEntity);
 
     }