A handover control device that conducts switching-over base station(s), in which a mobile station 111, . . . , 1NQ communicates, from one base station to another neighboring base station wherein a gateway server 30 monitors communication quality of the mobile station 111, . . . , 1NQ at a frequency according to a service level assigned to the mobile station 111, . . . , 1NQ and, if the communication quality falls below a predetermined quality, sends information on the another base station to the mobile station 111, . . . , 1NQ.