The present invention relates to a transmission rate control method of controlling a transmission rate of uplink user data to be transmitted from a mobile station to a radio base station. The method includes: starting to transmit at the mobile station, the uplink user data at an initial transmission rate which is informed from a network or an initial transmission rate which has been already informed from the network; and increasing at the mobile station the transmission rate of the uplink user data, up to a predetermined transmission rate, on a basis of a increase rule of the transmission rate which is beforehand determined.