To provide a low distortion amplifier which can obtain a high amplifying gain and can obtain a superior linear characteristic.

That the MOSFET amplifying circuit of an AB class has an opposite characteristic to the GaAsFET amplifier circuit of a C class is aimed and the characteristics of both circuits are synthesized. Thus, a high gain is realized. Namely, the GaAsFET amplifier circuit of the C class and the MOSFET amplifier circuit 12 of the AB class are connected in series. It is desirable that the MOSFET amplifier circuit of the AB class is arranged in an output stage and the GaAsFET amplifier circuit 11 of the C class is arranged in the driver stage preceding thereto.