Western people generally judge acts of commission as morally worse than equivalent acts of omission. This tendency is called "omission bias." This study examines whether omission bias occurs in Japanese. Participants were 43 Japanese undergraduate students. Five tasks were prepared. Each presented two stories with a similar structure but one key difference: the agent's act was either commission or omission. In one story, the agent did something causing a bad outcome; in the other story the agent did nothing causing the same bad outcome. The results showed that, in all five tasks, participants tended to judge that the agent who did something was morally worse than the agent who did nothing, but that participants also perceived that the do-something agent had stronger intention than the do-nothing agent in all five tasks. These results demonstrate omission bias in Japanese, which may occur by perceiving agents' intentions differently between commission and omission.