A base station receives signals transmitted from one terminal in cooperation with another base station and performs synthesis processing of the received signals of the other base station and the received signals of the local base station. In the base station, a determination circuit determines necessity of synthesis processing using the received signals of the local base station at the time of the first transmission of the terminal. A base station-to-base station communication circuit transmits a message requesting forwarding of the received signals to the other base station in a case where the synthesis processing is determined to be necessary and receives the forwarded signals that are forwarded from the other base station at the time of retransmission of the terminal. A synthesis circuit synthesizes the forwarded signals from the other base station and the received signals of the local base station in a case where the synthesis processing is determined to be necessary.