To provide an image rejection mixer with excellent performance being more stable compared with that of the conventional one, to provide an active poly-phase filter amplifier which is used for a circuit such as the image rejection mixer to improve the performance of the circuit, and also to provide mixer circuits.

The first and the second mixer circuits 13 and 14 are constituted of a Gilbert mixer with base-grounded differential amplifier inserted therein. Then a distortion characteristic is improved and OIP 3 is enhanced. First and second kinds of phase equipment 11 and 12 are constituted by using different types of poly-phase filters. When nonuniformity occurs in a constant number, a deviation in a phase rotation angle in each poly-phase filter is generated in a reverse direction. Thus, an excellent image rejection characteristic is kept concerning nonuniformity in the constant number of circuit elements.