The present invention performs an outer loop transmission power control in a more stable manner by preventing a status of being unable to detect an Enhanced Dedicated Physical Control Channel (E-DPCCH). A transmission power control method according to the present application includes: generating, at a mobile station UE, a transport block having a predetermined minimum transport block size, when information to be transmitted to a radio base station Node B does not exist; transmitting, from the mobile station UE to the radio base station Node B, the transport block by a transmission timing predetermined by a mobile communication system or a transmission timing notified from a radio network controller RNC; receiving, at the radio base station Node B, the transport block in accordance with the transmission timing; and controlling, at the radio base station Node B, the transmission power, according to a reception quality of the transport block.