PURPOSE: To provide the CMOS crystal oscillation circuit whose circuit integration is attained with high accuracy and having a stop function of the oscillation.

CONSTITUTION: A crystal oscillator H and a feedback resistor R of a crystal oscillator 31 are connected in parallel and both of parallel connecting points are connected to a low potential side power supply via each capacitor C. A CMOS inverter circuit 32 is an amplifier circuit for a crystal oscillation circuit by connecting both terminals of the crystal oscillator H between its input and output terminal. Control signals , inverse of from a control circuit 25 are inputted to transmission gates 21, 23 and gates of MOS transistors(TRs) 22, 24, and when the oscillation is made, the transmission gates 21, 23 are turned on and MOS TRs 22, 24 are turned off. When the oscillation is stopped, the transmission gates 21, 23 are turned off and the MOS TRs 22, 24 are turned on.