This study investigated the effect of the group norm on member's actual behavior tendency (the actual effect of the group norm). The participants were 108 employees of 2 factories (factory 1: n=37, factory 2: n=71). The group norms concerning arrival time to the work place were measured by the return potential model. Attendance behaviors were directly observed. Results were as follows. In the factors with stricter norm (factory 1), the proportions of attendance converged on an earlier time. In both factories, the proportions of attendance within the range of tolerable behavior (the actual e...