This study was designed to investigate the roles of gazing behavior during piano duo performance by highlighting coordination among performers. Experiment 1 was conducted under four conditions: invisible, only the body visible, only the head visible, and face -to -face. Experiment 2 was conducted under three conditions: invisible, only the movable head visible, and only the fixed head visible. In both experiments, performers looked toward each other just before temporal changes during coordination moments, which improved synchronization accuracy. The results also showed that gazing without movement cues to some extent facilitated synchronization, although asynchrony was greater under the restricted- movement condition than under the free- movement condition. The following results were obtained:(1) Mutual gaze is important for reducing timing lag between performers. (2) Mutual gaze modulates remarkable and arbitrary temporal expressions, such as fermata. (3) Performers may utilize movements as visual cues for strict synchronization.