A CDMA (Code Division Multiple Access) transmitter/receiver of the present invention includes a SIR (Signal-to-Interference Ratio) calculator for calculating SIRs of a received signal slot by slot. A command generating circuit generates, when the SIR decreases or increases, a transmission power control command that causes a station, which is sending the received signal, to lower or raise transmission power or generates, when the SIR continuously decreases over a preselected number of slots, a transmission power control-OFF command for interrupting transmission power control. The transmission power control command or the transmission power control-OFF command is inserted in a radio frame to be sent to the above station.