A mobile station apparatus in a CDMA/TDD mobile communication system employs a communication frame including a plurality of time slots. The time slots include a plurality of forward link time slots, disposed at regular intervals in the communication frame and assigned a common control channel. The time slots further include time slots other than the plurality of forward link time slots, divided into reverse link time slots and forward link time slots according to an amount of information on a forward link and on a reverse link. The mobile station apparatus includes a receiver that receives the communication frame including the plurality of time slots. A measurer measures individual reception qualities of the plurality of forward link time slots in the received communication frame including the forward link time slots assigned the common control channel. A weighter assigns a weight to each measured reception quality of the plurality of forward time slots. A transmission power controller performs transmission power control for reverse link time slots according to individual reception qualities of weighted forward link time slots.