A transmission rate control method for controlling transmission rate of uplink user data, including: notifying, at a radio network controller, a first correspondence of a transmission data block size of the uplink user data to a transmission wave amplitude ratio between an enhanced dedicated physical data channel and a dedicated physical control channel for the uplink user data, to a mobile station; generating, at the mobile station, a second correspondence of a transmission data block size of the uplink user data to a transmission power ratio between an enhanced dedicated physical data channel and a dedicated physical control channel for the uplink user data based on the notified first correspondence; notifying, at a radio base station, the transmission power ratio to the mobile station; and determining, at the mobile station, a transmission data block size of the uplink user data based on the notified transmission power ratio and the second correspondence.