When an H-ARQ is used for downlink high-speed packet transmission, appropriate transmit power control is performed on a retransmission packet for effective use of transmit power resources and reduced interference in a radio communication system, and the transmit power of the retransmission packets (transmission #2, transmission #3) is controlled to transmit power value so that the reception quality of the retransmission packets at the mobile station apparatus is lower than the reception quality of the initial transmission packet (transmission #1) at the mobile station apparatus. For example, the transmit power value of the retransmission packet is controlled to a value lower than the transmit power value of the initial transmission packet by a predetermined value X [dB].