A data flow amount control device in a mobile communication system 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 includes 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.