The object of the present invention is to provide a base station 10, a mobile station 11 and a radio network controller 50 which can reduce the load on the radio network controller 50 during multicast communication. The base station 10 supporting multicast communication comprises a response signal relay 10b configured to transfer response signals transmitted from a plurality of mobile stations 11, 12, 21, 41, 42 to a radio network controller 50. The response signals respond to a control signal for a multicast group. The response signal relay 10b transfers only a predetermined number of response signals to the radio network controller 50. Any following response signals are retained.