Each mobile terminal and/or radio base station determines whether a radio base station transmits radio waves of excessive power. Based on determination results obtained by a plurality of mobile terminals and/or radio base stations, a radio-system management server determines whether a certain radio base station transmits radio waves of excessive power. When the certain radio base station transmits radio waves of excessive power, the radio-system management server instructs the certain radio base station to forcefully stop its radio transmission by transmitting a forced transmission-stop control message to the radio network controller that controls the certain radio base station.