diff --git a/typing-server/api/handler/score.go b/typing-server/api/handler/score.go
index b061ab3..063d7d8 100644
--- a/typing-server/api/handler/score.go
+++ b/typing-server/api/handler/score.go
@@ -46,28 +46,26 @@ func GetScoresRanking(w http.ResponseWriter, r *http.Request) {
 func PostScore(w http.ResponseWriter, r *http.Request) {
 	ctx := r.Context()
 
-	userIDStr := r.URL.Query().Get("user_id")
-	userID, err := uuid.Parse(userIDStr)
-	if err != nil {
-		http.Error(w, "Invalid user_id", http.StatusBadRequest)
-		return
+	// リクエストボディから値を取得
+	var requestBody struct {
+		UserID     string  `json:"user_id"`
+		Keystrokes int     `json:"keystrokes"`
+		Accuracy   float64 `json:"accuracy"`
 	}
-
-	keystrokesStr := r.URL.Query().Get("keystrokes")
-	keystrokes, err := strconv.Atoi(keystrokesStr)
-	if err != nil {
-		http.Error(w, "Invalid keystrokes", http.StatusBadRequest)
+	if err := json.NewDecoder(r.Body).Decode(&requestBody); err != nil {
+		http.Error(w, "Invalid request body", http.StatusBadRequest)
 		return
 	}
 
-	accuracyStr := r.URL.Query().Get("accuracy")
-	accuracy, err := strconv.ParseFloat(accuracyStr, 64)
+	// user_idをUUIDに変換
+	userID, err := uuid.Parse(requestBody.UserID)
 	if err != nil {
-		http.Error(w, "Invalid accuracy", http.StatusBadRequest)
+		http.Error(w, "Invalid user_id", http.StatusBadRequest)
 		return
 	}
 
-	if err := service.CreateScore(ctx, entClient, userID, keystrokes, accuracy); err != nil {
+	// スコアを作成
+	if err := service.CreateScore(ctx, entClient, userID, requestBody.Keystrokes, requestBody.Accuracy); err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return
 	}
diff --git a/typing-server/api/repository/score.go b/typing-server/api/repository/score.go
index aa6ff5a..fadff4b 100644
--- a/typing-server/api/repository/score.go
+++ b/typing-server/api/repository/score.go
@@ -2,6 +2,7 @@ package repository
 
 import (
 	"context"
+	"database/sql"
 	"fmt"
 
 	"github.com/google/uuid"
@@ -90,10 +91,27 @@ func GetScoresRanking(ctx context.Context, client *ent.Client, sortBy string, st
 
 	return rankings, nil
 }
-
 func CreateScore(ctx context.Context, client *ent.Client, userID uuid.UUID, keystrokes int, accuracy float64) error {
-	// Create a new score
-	createdScore, err := client.Score.Create().
+	// トランザクションを開始
+	tx, err := client.Tx(ctx)
+	if err != nil {
+		return err
+	}
+	defer func() {
+		// txがコミット済みの場合はロールバックしない
+		if tx == nil {
+			return
+		}
+		if err := tx.Rollback(); err != nil {
+			if err != sql.ErrTxDone {
+				return
+			}
+			return
+		}
+	}()
+
+	// 新しいスコアを作成
+	createdScore, err := tx.Score.Create().
 		SetKeystrokes(keystrokes).
 		SetAccuracy(accuracy).
 		SetUserID(userID).
@@ -102,46 +120,70 @@ func CreateScore(ctx context.Context, client *ent.Client, userID uuid.UUID, keys
 		return err
 	}
 
+	// キーストロークと精度のチェック
 	if keystrokes < 120 || accuracy < 0.95 {
-		return nil
+		return tx.Commit()
 	}
 
-	// Get the user
-	user, err := client.User.Query().Where(user.ID(userID)).Only(ctx)
+	// ユーザーを取得
+	user, err := tx.User.Query().Where(user.ID(userID)).Only(ctx)
 	if err != nil {
 		return err
 	}
 
-	// Check if the new score has the maximum keystrokes
+	// 最大キーストロークと最大精度のスコアを取得
+	maxKeystrokeScore, maxAccuracyScore, err := getMaxScores(ctx, user)
+	if err != nil {
+		return err
+	}
+
+	// 以前の最大スコアのフラグを更新
+	err = updateMaxScoreFlags(ctx, maxKeystrokeScore, maxAccuracyScore, createdScore)
+	if err != nil {
+		return err
+	}
+
+	// トランザクションをコミット
+	return tx.Commit()
+}
+
+func getMaxScores(ctx context.Context, user *ent.User) (*ent.Score, *ent.Score, error) {
+	// 最大キーストロークのスコアを取得
 	maxKeystrokeScore, err := user.QueryScores().Where(score.IsMaxKeystrokes(true)).Only(ctx)
 	if err != nil && !ent.IsNotFound(err) {
-		return err
+		return nil, nil, err
 	}
-	isMaxKeystrokes := maxKeystrokeScore == nil || createdScore.Keystrokes >= maxKeystrokeScore.Keystrokes
 
-	// Check if the new score has the maximum accuracy
+	// 最大精度のスコアを取得
 	maxAccuracyScore, err := user.QueryScores().Where(score.IsMaxAccuracy(true)).Only(ctx)
 	if err != nil && !ent.IsNotFound(err) {
-		return err
+		return nil, nil, err
 	}
+
+	return maxKeystrokeScore, maxAccuracyScore, nil
+}
+
+func updateMaxScoreFlags(ctx context.Context, maxKeystrokeScore, maxAccuracyScore, createdScore *ent.Score) error {
+	isMaxKeystrokes := maxKeystrokeScore == nil || createdScore.Keystrokes >= maxKeystrokeScore.Keystrokes
 	isMaxAccuracy := maxAccuracyScore == nil || createdScore.Accuracy >= maxAccuracyScore.Accuracy
 
-	// Update the flags of the previous maximum scores
-	if maxKeystrokeScore != nil && !isMaxKeystrokes {
-		err = maxKeystrokeScore.Update().SetIsMaxKeystrokes(false).Exec(ctx)
+	// 以前の最大スコアのフラグを更新
+	if maxKeystrokeScore != nil && isMaxKeystrokes {
+		err := maxKeystrokeScore.Update().SetIsMaxKeystrokes(false).Exec(ctx)
 		if err != nil {
 			return err
 		}
 	}
-	if maxAccuracyScore != nil && !isMaxAccuracy {
-		err = maxAccuracyScore.Update().SetIsMaxAccuracy(false).Exec(ctx)
+
+	if maxAccuracyScore != nil && isMaxAccuracy {
+		err := maxAccuracyScore.Update().SetIsMaxAccuracy(false).Exec(ctx)
 		if err != nil {
 			return err
 		}
 	}
 
-	// Update the score with the maximum flags
-	err = createdScore.Update().
+	// 作成したスコアの最大フラグを更新
+	err := createdScore.Update().
 		SetIsMaxKeystrokes(isMaxKeystrokes).
 		SetIsMaxAccuracy(isMaxAccuracy).
 		Exec(ctx)