A transmission rate control method for controlling a transmission rate of data transmitted from a mobile station to a radio base station via an uplink, includes: receiving, at the mobile station, an Absolute Rate Grant Channel which indicates an absolute value of the transmission rate from the radio base station; and ignoring, at the mobile station, a Relative Rate Grant Channel which indicates a relative value of the transmission rate until each HARQ process has been performed once, after receiving the Absolute Rate Grant Channel.