Disclosed is a power amplifier apparatus including: an amplifier amplifying an input modulated signal; a control signal generator receiving an amplitude component of the input modulated signal and generating a control signal; and a power combiner performing ON/OFF control of a switching element based on the control signal to control conduction and non-conduction of a current supplied from a second power supply. In the power combiner, a power of a pulsed form when the current from the second power supply is conductive is transferred in a direction of a first power supply, using a transformer. A difference power obtained by subtracting a constant value from a first power supply voltage when the amplitude of the input modulated signal is smaller than that of a reference signal is supplied from the power combiner to the amplifier, as a power supply thereof (FIG. 1).