AimThe aim of our study was to clarify the geographical movement of patients treated in psychiatric facilities, which can provide important information on the resources and health-care system of psychiatric services. MethodsWe conducted an analysis of nationwide data on psychiatric patients, collected as an additional survey to the conventional 630 survey' in 2014. For the 151 848 initially admitted inpatients during 6 months and the 144 401 outpatients on a specific day, we identified whether a patient was admitted to a psychiatric facility located in the same medical area as his/her residence. We estimated percentages of being from (i) within the medical area, (ii) within the prefecture, and (iii) outside the prefecture, using a Bayesian statistical approach for each secondary medical area. ResultsThe inpatients moved across wider areas than did the outpatients. Almost all inpatients and outpatients received their medical treatment at hospitals/clinics within their prefecture of residence. ConclusionThe current mental health medical system in Japan has been operating according to prefecture unit; thus, it may be appropriate to plan a medical system at a prefectural level.