To provide a CR oscillation circuit of an accurate oscillation frequency even if a threshold voltage of an MOS transistor (hereinafter simply referred to as MOS by omitting transistor) varies.

A resistance 1 and a capacitor 2 are connected between a power supply terminal Vcc and a ground. PMOS 3, 4 wherein a gate is connected parallel in the connection point, and a drain and a source of NMOS 6, 7 are connected in series between the power supply terminal Vcc and the ground. Furthermore, a source of a PMOS 5 is connected to a connection point of a drain/source of the PMOS 3, 4, a gate is connected to a connection point of a drain of the PMOS 4 and the NMOS 6 and a drain is connected to a gate of an NMOS 8. A drain of the NMOS 8 is connected to the power supply terminal Vcc and a source is connected to a connection point of a source/drain of the NMOS 6, 7. Output thereof is connected to a gate of an NMOS 9 whose drain/source are connected to both ends of a capacitor 2 through an inverter 10.