diff --git a/typing-server/api/repository/score.go b/typing-server/api/repository/score.go
index aa6ff5a..417449c 100644
--- a/typing-server/api/repository/score.go
+++ b/typing-server/api/repository/score.go
@@ -90,10 +90,20 @@ 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() {
+		if r := recover(); r != nil {
+			tx.Rollback()
+		}
+	}()
+
+	// 新しいスコアを作成
+	createdScore, err := tx.Score.Create().
 		SetKeystrokes(keystrokes).
 		SetAccuracy(accuracy).
 		SetUserID(userID).
@@ -102,46 +112,70 @@ 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()
+	}
+
+	// ユーザーを取得
+	user, err := tx.User.Query().Where(user.ID(userID)).Only(ctx)
+	if err != nil {
+		return err
+	}
+
+	// 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
 	}
 
-	// Get the user
-	user, err := client.User.Query().Where(user.ID(userID)).Only(ctx)
+	// 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
 	}
 
-	// Check if the new score has the maximum keystrokes
+	// 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)