diff --git a/backend/src/main/java/com/example/todoapp/controller/RecipesController.java b/backend/src/main/java/com/example/todoapp/controller/RecipesController.java
index b2f97ab..6156ba5 100644
--- a/backend/src/main/java/com/example/todoapp/controller/RecipesController.java
+++ b/backend/src/main/java/com/example/todoapp/controller/RecipesController.java
@@ -8,6 +8,7 @@ import java.util.stream.Collectors;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.core.Authentication;
+import org.springframework.security.core.userdetails.UsernameNotFoundException;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.PutMapping;
 import org.springframework.web.bind.annotation.RequestBody;
@@ -18,6 +19,8 @@ import com.example.todoapp.dto.RecipeDetailDTO;
 import com.example.todoapp.dto.RecipeRequestDTO;
 import com.example.todoapp.dto.RecipeResponseDTO;
 import com.example.todoapp.model.Recipes;
+import com.example.todoapp.model.User;
+import com.example.todoapp.repository.UserRepository;
 import com.example.todoapp.service.RecipeService;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.RequestParam;
@@ -36,6 +39,9 @@ public class RecipesController {
     @Autowired
     private RecipeService recipeService;
 
+    @Autowired
+    private UserRepository userRepository;
+
     /**
      * 新しいレシピを作成する
      *
@@ -62,7 +68,12 @@ public class RecipesController {
      */
     @GetMapping("/getAll")
     public ResponseEntity<List<RecipeResponseDTO>> getRecipe(Authentication authentication) {
+        
+        User user = userRepository.findByUsername(authentication.getName())
+            .orElseThrow(() -> new UsernameNotFoundException("User not found"));
+        
         List<Recipes> recipes = recipeService.getAllRecipes();
+
         // エンティティからDTOへの変換
         List<RecipeResponseDTO> responseList = recipes.stream()
             .map(recipe -> {
@@ -70,6 +81,7 @@ public class RecipesController {
                 dto.setRecipeId(recipe.getRecipeId()); 
                 dto.setRecipeName(recipe.getRecipeName());
                 dto.setSummary(recipe.getSummary());
+                dto.setMaxServings(recipeService.getRecipeMaxServings(user.getId(), recipe));
                 return dto;
         })
         .collect(Collectors.toList());
diff --git a/backend/src/main/java/com/example/todoapp/dto/RecipeResponseDTO.java b/backend/src/main/java/com/example/todoapp/dto/RecipeResponseDTO.java
index 38d69a3..b8d6887 100644
--- a/backend/src/main/java/com/example/todoapp/dto/RecipeResponseDTO.java
+++ b/backend/src/main/java/com/example/todoapp/dto/RecipeResponseDTO.java
@@ -28,4 +28,10 @@ public class RecipeResponseDTO {
      * レシピの簡単な説明文
      */
     private String summary;
+
+    /**
+     * 最大調理可能数
+     * そのレシピを何人分調理可能か
+     */
+    private int maxServings;
 }
diff --git a/backend/src/main/java/com/example/todoapp/repository/ToBuysRepository.java b/backend/src/main/java/com/example/todoapp/repository/ToBuysRepository.java
index 0778f5f..24d464f 100644
--- a/backend/src/main/java/com/example/todoapp/repository/ToBuysRepository.java
+++ b/backend/src/main/java/com/example/todoapp/repository/ToBuysRepository.java
@@ -47,6 +47,17 @@ public interface ToBuysRepository extends JpaRepository<ToBuys, Integer> {
      */
     @Query("SELECT t FROM ToBuys t WHERE t.user.id = :userId ORDER BY t.tobuyId ASC")
     List<ToBuys> findByUserIdOrderByTobuyIdAsc(@Param("userId") Long userId);
+    
+    /**
+     * 指定された「買うもの」IDに基づいて「買うもの」での数量を更新
+     *
+     * @param tobuyId 「買うもの」ID
+     * @param amount 「買うもの」数量
+     * @return 更新された行数
+     */
+    @Modifying
+    @Query("UPDATE ToBuys t SET t.amount = :amount WHERE t.tobuyId = :tobuyId")
+    int updateAmountByTobuyId(Long tobuyId, int amount);
 
     /**
      * 指定された「買うもの」IDに基づいて「買うもの」リストを削除
diff --git a/backend/src/main/java/com/example/todoapp/service/RecipeService.java b/backend/src/main/java/com/example/todoapp/service/RecipeService.java
index 3329420..ad27f08 100644
--- a/backend/src/main/java/com/example/todoapp/service/RecipeService.java
+++ b/backend/src/main/java/com/example/todoapp/service/RecipeService.java
@@ -49,6 +49,9 @@ public class RecipeService {
     @Autowired
     private RecipeStuffsRepository recipeStuffsRepository;
 
+    @Autowired
+    private StocksService stockService;
+
     /**
      * レシピを新規登録する
      *
@@ -102,6 +105,34 @@ public class RecipeService {
         return recipesRepository.findAll();
     }
 
+    /**
+     * レシピを指定して，現在の在庫を参照しそのレシピが最大何人分作れるか返す
+     * 
+     * @param userId ユーザーID
+     * @param recipe レシピのエンティティ
+     * @throws RuntimeException レシピが材料を持たないなど，計算に失敗したとき
+     * @return 最大何人分作れるか
+     */
+    public int getRecipeMaxServings(Long userId, Recipes recipe) {
+
+        List<RecipeStuffs> recipeStuffs = recipeStuffsRepository.findByRecipesRecipeId(recipe.getRecipeId());
+
+        //  各材料がその料理のレシピで何人分在庫があるか計算し，それらの最小値が料理全体での人数になる
+        Integer minNServings = null;
+        for (RecipeStuffs recipeStuff : recipeStuffs) {
+            int stockAmount = stockService.calcAmountByStuffId(userId, recipeStuff.getStuff().getStuffId());
+            int nServings = stockAmount / recipeStuff.getAmount(); // 小数点以下切り捨て（整数除算）
+            if (minNServings == null || minNServings > nServings) {
+                minNServings = nServings;
+            }
+        }
+
+        //  recipeStuffs が空の場合などに null のままになる（通常は起こりえない）
+        if (minNServings == null) throw new RuntimeException("Failed to calculate recipeMaxServings");
+
+        return minNServings;
+    }
+
     /**
      * 指定されたIDのレシピ詳細情報を取得する
      *
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 d88d629..ddf5681 100644
--- a/backend/src/main/java/com/example/todoapp/service/ToBuysService.java
+++ b/backend/src/main/java/com/example/todoapp/service/ToBuysService.java
@@ -174,6 +174,16 @@ public class ToBuysService {
         return toBuysRepository.findByUserIdOrderByTobuyIdAsc(user.getId());
     }
 
+    /**
+     * 指定された購入リストIDに基づいて「数量」を変更する
+     *
+     * @param tobuyId 購入リストID
+     */
+    @Transactional
+    public int updateToBuysAmountByTobuyId(Long tobuyId, int amount) {
+        return toBuysRepository.updateAmountByTobuyId(tobuyId, amount);
+    }
+
     /**
      * 指定された購入リストIDに基づいて「買うもの」を削除する
      *
@@ -210,9 +220,17 @@ public class ToBuysService {
         stock.setBuyDate(dto.getBuyDate());
         stock.setExpDate(dto.getExpDate());
 
-        // 買うものリストから削除
+        // まだ買うべき数量を計算
+        int remainAmount = Math.max(tobuy.getAmount() - dto.getAmount(), 0);
+        System.out.println("remainAmount=" + remainAmount);
+
+        // 買うものリストから削除または数量変更
         System.out.println("tobuy.getTobuyId()=" + tobuy.getTobuyId());
-        deleteToBuysByTobuyId(tobuy.getTobuyId());
+        if (remainAmount > 0) {
+            updateToBuysAmountByTobuyId(tobuy.getTobuyId(), remainAmount);
+        } else {
+            deleteToBuysByTobuyId(tobuy.getTobuyId());
+        }
 
         // データベースに保存
         return stocksRepository.save(stock);
diff --git a/frontend/src/services/api.ts b/frontend/src/services/api.ts
index 8aacbc6..72a1094 100644
--- a/frontend/src/services/api.ts
+++ b/frontend/src/services/api.ts
@@ -456,7 +456,12 @@ export const recipeApi = {
         errorData?.message
       );
     }
-    return response.json();
+
+    //  デバッグ用に表示
+    const recipes = response.json();
+    console.log('recipes: ', recipes);
+
+    return recipes;
   },
 
   /**
diff --git a/frontend/src/types/types.ts b/frontend/src/types/types.ts
index bd64d97..dc970d7 100644
--- a/frontend/src/types/types.ts
+++ b/frontend/src/types/types.ts
@@ -142,7 +142,8 @@ export interface Recipe {
 }
 
 export interface RecipeWithId extends Recipe {
-  recipeId: number;
+  recipeId: number; // レシピID
+  maxServings: number; // 最大調理可能数
 }
 
 /**