Between an output terminal (drain terminal) of a semiconductor device in a first unit amplifier and an output port, a -90 degrees phase-shift circuit is connected, while between an output terminal (drain terminal) of a semiconductor device in a second unit amplifier and the output port, a +90 degrees phase-shift circuit is connected. Between the first and second ports, there is inserted a series circuit made up of first and second inductance components with an almost identical size. Then, to a middle point between the first and second inductance components, a bias feed terminal is connected, and between the middle point and a ground, a series circuit made up of a resistance component and a capacitance component is connected. The small-size balanced amplifier circuit can perform accurate balance operation in wide bands.