Nowadays, communication robots are becoming popular since they are actively used in both commercially and personally. Increasing empathy between human-robot can effectively enhance the positive impression. Empathy can be created by syncing human emotion with the robot expression. Emotion estimation can be done by analyzing controllable expressions like facial expression, or uncontrollable expression like biological signals. In this work, we propose the comparison of robot expression synchronization with estimated emotion based on either facial expression or biological signal. In order to find out which of the proposed methods yield the best impression, subjective impression rating is used in the experiment. From the result of the impression evaluation, we found that the robot’s facial expression synchronization using the synchronization based on periodical emotion value performs the best and best suitable for emotion estimated both from facial expression and biological signal.