The present invention allows a gain control to be appropriately effected even when a frame including no preamble signal block is used for wireless communications. The following processes are effected in a transmission power control unit 106 of a transmission unit. Specifically, an automatic transmission gain control unit 201 multiplies a transmission signal by a gain value that is the difference between the power of a signal loop-backed from a power amplifier 109 and the power of the transmission signal. A fixed transmission gain multiplying unit 202 multiplies the transmission signal by a predetermined gain value or by the gain value used in the automatic transmission gain control unit 201 during the preceding frame. A selection unit 203 selects the transmission signal as gain-controlled by the automatic transmission gain control unit 201 in a case of a preamble signal block being included in the frame of the transmission signal and selects the transmission signal as gain-controlled by the fixed transmission gain multiplying unit 202 in a case of no preamble signal block being included in the frame of the transmission signal.