The Bureau of Social Welfare attached to the Tokyo Municipal Office managed the municipal baths as a part of its social welfare services from 1923 to 1940. This paper first shows how public baths developed into urban sanitary facilities-as the regulation regarding the handling of water in the public baths became stricter-by the time the bureau began the service. The paper then analyses the way the bureau operated the municipal baths, and, through the examination, it is found that the bureau clearly recognized the public baths as urban sanitary facilities.