A transmission rate control method for controlling, at a mobile station, a transmission rate of uplink user data, in a radio communication system capable of controlling a transmission rate of uplink user data based on an absolute transmission rate transmitted via an E-AGCH and a relative transmission rate transmitted via a E-RGCH, includes: notifying, from a radio network controller to the mobile station, information for identifying the E-AGCH to be transmitted from a serving cell, and not notifying, from the radio network controller to the mobile station, information for identifying the E-RGCH, when the mobile station establishes an E-DPDCH; and controlling, at the mobile station, the transmission rate of uplink user data, based on the absolute transmission rate which is received from the serving cell via the E-AGCH, without considering the relative transmission rate.