In a mobile communication system in which a plurality of base stations included in a CoMP cooperating set perform downlink CoMP communication with a user terminal, each of the plurality of base stations comprises: a first transmission unit that transmits first transmission data in each of a plurality of HARQ processes; and a retransmission unit that transmits retransmission data corresponding to the first transmission data in each of the plurality of HARQ processes, and a transmission interval of the first transmission data by the first transmission unit is set to a minimum odd number larger than a maximum HARQ retransmission number.