The present invention relates to a transmission power control method which controls a transmission power of uplink user data for transmitting an uplink user data from a mobile station to a radio base station. The transmission power control method according to the present invention includes: transmitting, from the mobile station to the radio base station, a transmission data block which includes control information periodically, even when user data to be transmitted has not existed in a transmission buffer of the mobile station; notifying, at the radio base station, the number of retransmissions of the transmission data block, to a radio network controller; determining, at the radio network controller, a target SIR of a dedicated physical control channel in the radio base station based on the notified number of retransmissions and notifying the determined target SIR to the radio base station; controlling, at the radio base station, a transmission power of the dedicated physical control channel in the mobile station based on the notified target SIR; and determining, at the radio network controller, a transmission wave amplitude ratio between the uplink user data channel and the dedicated physical control channel based on the notified number of retransmissions and notifying the determined transmission wave amplitude ratio to the mobile station.