A base station accommodation method and mobile communication system which allows the installation of many micro-miniature BTS devices are provided. The mobile communication system includes a plurality of base stations which accommodate a plurality of mobile terminals respectively; a plurality of first base station control devices, each of which accommodates a predetermined number of base stations out of the plurality of base stations; and a second base station control device which accommodates the plurality of first base station control devices, wherein each of the plurality of first base station control devices comprises, for supporting information identifying a mobile terminal, a mobile terminal data base to store identification information which identifies a base station to which the mobile terminal is subordinate, and a station data base to store an address of the base station.