A mobile communication method includes: causing a cell under control of a radio base station to determine an initial granted value when an uplink user data transmission channel is set up between a mobile station and the cell under the control of the radio base station; causing a radio network controller to notify the mobile station of the initial granted value determined by the cell under the control of the radio base station; and causing the mobile station to transmit uplink user data via the uplink user data transmission channel at a transmission rate corresponding to the initial granted value after the uplink user data transmission channel is set up, and the cell under the control of the radio base station sets the initial granted value to be equal to the granted value used in transmitting only a single data unit on the uplink user data transmission channel.