diff --git a/backend/src/main/java/com/example/todoapp/controller/ToBuysController.java b/backend/src/main/java/com/example/todoapp/controller/ToBuysController.java
index b984698..bce8a33 100644
--- a/backend/src/main/java/com/example/todoapp/controller/ToBuysController.java
+++ b/backend/src/main/java/com/example/todoapp/controller/ToBuysController.java
@@ -52,8 +52,10 @@ public class ToBuysController {
      */
 
     @PostMapping("/add")
-    public ResponseEntity<String> addToBuys(@Valid @RequestBody ToBuysDTO dto) {
-        toBuysService.addToBuys(dto);
+    public ResponseEntity<String> addToBuys(
+        @Valid @RequestBody ToBuysDTO dto, 
+        Authentication authentication) {
+        toBuysService.addToBuys(dto, authentication);
         return ResponseEntity.ok("Item added to 'To Buys' successfully");
     }
 
@@ -66,11 +68,10 @@ public class ToBuysController {
     @GetMapping("/get")
     public ResponseEntity<?> getAllToBuysByUserId(Authentication authentication) {
 
-    
         // 認証されたユーザー名を取得
         String username = authentication.getName();
 
-        // ユーザー情報を取得（例: userRepository経由）
+        // ユーザー情報を取得
         User user = userRepository.findByUsername(username)
                 .orElseThrow(() -> new UsernameNotFoundException("User not found"));
 
@@ -102,8 +103,18 @@ public class ToBuysController {
      * @return 削除が成功した場合にtrueを含むレスポンス
      */
     @DeleteMapping("/delete")
-    public ResponseEntity<Map<String, Boolean>> deleteToBuy(@RequestBody DeleteToBuyRequest request) {
-        int deletedCount = toBuysService.deleteToBuyByIds(request.getUser_id(), request.getTobuy_id());
+    public ResponseEntity<Map<String, Boolean>> deleteToBuy(
+        @RequestBody DeleteToBuyRequest request,
+        Authentication authentication) {
+            
+        // 認証されたユーザー名を取得
+        String username = authentication.getName();    
+        
+        // ユーザー情報を取得
+        User user = userRepository.findByUsername(username)
+                .orElseThrow(() -> new UsernameNotFoundException("User not found"));
+        
+        int deletedCount = toBuysService.deleteToBuyByIds(user.getId(), request.getTobuy_id());
 
         Map<String, Boolean> response = new HashMap<>();
 
diff --git a/backend/src/main/java/com/example/todoapp/service/ToBuysService.java b/backend/src/main/java/com/example/todoapp/service/ToBuysService.java
index 589137c..8049ee9 100644
--- a/backend/src/main/java/com/example/todoapp/service/ToBuysService.java
+++ b/backend/src/main/java/com/example/todoapp/service/ToBuysService.java
@@ -18,6 +18,7 @@ import com.example.todoapp.repository.UserRepository;
 
 import jakarta.transaction.Transactional;
 
+import org.springframework.security.core.Authentication;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
 
@@ -50,11 +51,12 @@ public class ToBuysService {
      *
      * @param toBuyDTO 追加する購入アイテムのデータ（DTO）
      */
-    public void addToBuys(ToBuysDTO toBuyDTO) {
+    public void addToBuys(ToBuysDTO toBuyDTO, Authentication authentication) {
 
         // ユーザー情報を取得
-        User user = userRepository.findById(toBuyDTO.getUser_id())
-                .orElseThrow(() -> new RuntimeException("ユーザーがありませ: " + toBuyDTO.getUser_id()));
+        String username = authentication.getName();
+        User user = userRepository.findByUsername(username)
+                .orElseThrow(() -> new RuntimeException("ユーザーが見つかりません: " + username));
 
         Stuffs stuffs;
         if (toBuyDTO.getStuff_id() == null) {