PURPOSE: To improve a CMOS output circuit in output characteristics by a method wherein a means which controls a PMOS and an NMOS output transistor in effective channel width and another means which enables the output transistors to generate control signals are provided.

CONSTITUTION: A primary component part is composed of a PMOS output transistor 4, an NMOS output transistor 5, effective channel width control means 6 and 7, and a control circuit block 3. When signals of H level and L level are inputted into control input terminals 9a and 9b respectively, the control circuit block 3 is degraded in drive capacity by one rank, and when signal of H level is inputted into both the terminals 9a and 9b, transistors 6T1 and 6T2 are turned OFF and the control circuit block 3 is kept low in drive capacity. When signal of L level is inputted into both the terminals 9a and 9b, transistors 7T1 and 7T2 are turned ON and the control circuit block 3 is kept high in drive capacity. By this setup, an output transistor can be controlled in current drive capacity.