In the present research, first we evaluated the association between urban area size and commuting modes with physical activity among working people. Then we investigated the longitudinal effects of urban area size and commuting modes on increased physical activity due to health guidance intervention. The subjects were 401 male employees (aged 46.3±7.8) of A corporation, and were split into two groups, metropolitan area group (N=235) and local area group (N=166), based on the population density of place of work. IPAQ-E was used for evaluation of walking environments, and physical activity was assessed using pedometers. The intervention consisted of an exercise-focused health guidance over the course of one year. The cross-sectional study admitted that in comparison with the local area group the metropolitan area group had more than physical activity (p<0.01). Not only the size of urban area but commuting modes were significantly related to the level of daily physical activity (p<0.001). In longitudinal study, regarding the effects of the intervention for the physical activity, the study showed the possibility that urban area size was not directly effective but traffic safety in residential area (p<0.05) and willingness to take a walk (p<0.01) were effective. The cross-sectional study suggested that the size of the urban area and commuting modes had independently an effect on the physical activity of working people. The longitudinal study, on the other hand, suggested that the size of the urban area and commuting modes may not any direct influence on the effects of physical activity intervention.