A transmission rate control method for controlling transmission rate of layer-2 control information, including: notifying, at a radio network controller, a correspondence of a transmission data blocksize of the layer-2 control information to a transmission power ratio between an enhanced dedicated physical data channel and a dedicated physical control channel on the layer-2 control information, to a mobile station; determining, at the mobile station, a transmission power ratio of the layer-2 control information to be transmitted based on the correspondence; and transmitting, at the mobile station, the layer-2 control information using the determined transmission power ratio.