A transmitter receiver unit of the present invention comprises a phase shifter connected between a transistor and a filter multiplexer for decreasing a reactance component of an impedance, as observed from the transistor toward the filter multiplexer, to a value close to zero in a third frequency band given as the sum or difference between the integer multiples of a second frequency band and a first frequency band. This structure decreases the impedance in the third frequency band of the filter multiplexer side as observed from the transistor, thereby making the transistor not liable to generate a signal voltage of the third frequency band.