In this study, I examine whether differences in the levels of stress exist with regard to the police department size. To accomplish this, a way ANOVA analysis of variance(One-way ANOVA) was conducted. As a result, a significant difference was found in Job stress and traumatic stress according to the department size and grade. Specifically, first, in the job stress level on the department size, the smaller department size was, the higher job stress level was and the bigger department size was, the lower job stress level was. Second, in the traumatic stress level on the department size, the smaller department size was, the higher traumatic stress level was and the bigger department size was, the lower traumatic stress level was. Third, in the job stress level on the department grade, the lower department grade was, the lower job stress level was and the higher department grade was, the higher job stress level was. Fourth, in the traumatic stress level on the department grade, the lower department grade was, the lower traumatic stress level was and the higher department grade was, the higher traumatic stress level was.