The present invention relates to a data flow amount control device in a mobile communication system, which includes a plurality of mobile stations, a control station relaying packets to each of the plurality of mobile stations, and a base station temporarily storing the packets transmitted from the control station in a buffer and transmitting the packets to each of the plurality of mobile stations. The data flow amount control device comprises a radio condition acquisition unit configured to acquire a radio condition of each of the plurality of mobile stations; a packet transmission frequency calculation unit configured to calculate a transmission frequency of the packets transmitted from the base station to each of the plurality of mobile stations; and a packet transmission amount control unit configured to control a transmission amount of the packets transmitted from the control station to the base station, according to the radio condition of each of the plurality of mobile stations and the transmission frequency of the packets transmitted from the base station to each of the plurality of mobile stations.