A transmission rate control method, includes: transmitting, at a radio base station, a relative rate grant channel which includes a command for controlling a transmission rate in uplink to a mobile station; and determining, at the mobile station, that the relative rate grant channel which includes a HOLD command for instructing to maintain the transmission rate is received at the mobile station, when data to be transmitted becomes empty in a transmission buffer and a receive signal in the relative rate grant channel is detected as “0” or “+1”, and maintaining the transmission rate.