The objectives of this study were to verify the determinants of regular exercise behavior in female workers by applying a modified Theory of Planned Behavior. The variables investigated for this study were health status, health concern, health habit, attitude (7 items), subjective norm (3 items), and perceived behavioral control(5 items). Data was collected from 204 female workers using a self-administered questionnaire. The results of this study were as follows. 1) Regular exercise behavior was significantly influenced by perceived behavior control for time, pleasurable attitude, and the subjective norm of their colleagues. 2) A modified Theory of Planned Behavior is particularly useful in explaining exercise behavior of female workers. We suggest that health care providers should focus on not only attitude and social norms but also perceived behavioral control in order to improve the exercise behavior of female workers.