A mobile communication system having plural base stations and a radio controller configured to control each of the base stations is disclosed. Each of the base stations has a transmission power notifying unit which notifies the radio controller of downlink transmission power to mobile stations. The radio controller includes a cell determination unit which determines one cell having good communications quality among cells provided by each of the base stations; a reference power ratio decision unit which decides a reference power ratio based on the ratio of the downlink transmission power to the maximum transmission power of the base station providing the determined cell; and a reference power ratio notifying unit which notifies each of the base stations of the decided reference power ratio. Each of the base stations additionally has a transmission power controller which controls the downlink transmission power so that the ratio of the downlink transmission power to its maximum transmission power to mobile stations approaches the reference power ratio.