A power amplifier able to minimize the deterioration of the linearity with respect to fluctuations in ambient temperature, wherein a first terminal of a first resistance element and a first terminal of a second resistance with a temperature coefficient smaller than that of the first resistance element are connected, the connection point is connected to a gate terminal of an FET, a second terminal of the first resistance element is connected to a bias voltage supply terminal, a second terminal of the second resistance element is connected to the ground potential, a drain terminal of the FET is connected to a power source voltage supply terminal, a source terminal is connected to the ground potential, and the FET and the first resistance element are constituted by semiconductor devices formed on the same semiconductor substrate.