The present invention relates to a mobile station apparatus and a transmission power control method for the same apparatus, capable of improving the decision accuracy in a mobile station with respect to a TPC command from a base station to the mobile station and of maintaining the optimum transmission power. In the mobile station which is made to control the transmission power to the base station on the basis of a TPC command received from the base station, a plurality of TPC commands received from a plurality of base stations are weighting-combined so as to control the transmission power to the base stations on the basis of a result of the weighting combination.