The authors investigated the effect of gaze tracking by agent for human. Psychological study has shown that presence of others facilitates efforts of working partner. This effect also occurs if the presence of others replaced to robot. Furthermore, previous research shows that the effects on a person being touched by a robot to motivate him or her. However, direct contact such as touch with robot has a risk of disturbing human work. The authors use gaze tracking for social facilitation, because gaze tracking can also facilitate human efforts. The authors implemented social facilitation robot agent by using gaze tracking. The agent projects its face on the surface to show quickly changing expression which is difficult for achieve by ordinally robots. The agent also can express gaze tracking by implemented eye trackers. The authors prepared three conditions with monotonous task for comparing the effect of gaze tracking, first: the agent gazes the aim of task, second: the agent moves its gaze randomly, third: the agent traces the gaze point of participant. The result showed that the participant raise motivation if the agent traces gazed point by human, even though there are no the different on achievement score of task and continuation time.