A base station of a mobile communication system which allocates a bandwidth for handover ranging or bandwidth request ranging in response to a code transmitted from a mobile station that is selected by the mobile station from a plurality of codes includes a ranging allocating unit configured to allocate, to a mobile station performing handover, at least one of a dedicated ranging code and a dedicated ranging slot that are exclusively used and not used by any mobile stations other than the mobile station, and that are provided separately for each of a plurality of base stations to which the mobile station is to be possibly connected.