In a class AB CMOS output circuit provided with a CMOS circuit including first P and N channel transistors and operating by a predetermined operating current Io, a replica circuit is formed on a semiconductor substrate of the CMOS circuit, and includes a second P channel transistor having a size equal or similar to that of the first P channel transistor, and a second N channel transistor having a size equal or similar to that of the first N channel transistor. A bias voltage supply allows the second P and N channel transistors to operate based on a reference current Iref corresponding to the operating current Io, applies a first bias voltage as applied to the second P channel transistor to the first P channel transistor, and applies a second bias voltage as applied to the second N channel transistor to the first N channel transistor.