The present study investigated the determinant of compliant conforming behaviour from the viewpoint of the self-monitoring. Subjects, who were classified into High Self-Monitors (HSM) and Low Self-Monitors (LSM), participated in the experiment in which they had a task to distinguish the size of two circles. About the half of subjects performed the task with confederates. In eight of 13 trials, confederates had mistaken distinctions intentionally. The results showed HSM were more conformable to confederates than LSM for male subjects. HSM seemed to conform themselves to confederates easily, because their behaviour was guided by external cues. By contrast, LSM would conform themselves with difficulty, because their behaviour was guided by their internal states. But there were no significant differences for female subjects, and the ability of self-monitoring was considered as the less explanatory determinant for conformity in this experiment.