In a power amplifier, in response to a power mode signal at a predetermined level, a first switch circuit supplies a signal to first and second amplifier devices that perform parallel operations. In response to the power mode signal at another level, the first switch circuit supplies a signal to the first amplifier device and stops supplying the signal to the second amplifier device such that the first amplifier device performs a standalone operation. One end of an impedance adjusting circuit is connected to a connection node between the outputs of the first and second amplifier devices, the other end of the impedance adjusting circuit is connected to one end of a second switch circuit, and the other end of the second switch circuit is connected to a ground potential. The impedance adjusting circuit includes a reactance element.