To obtain a circuit suitably suppressing abnormal oscillation due to spurious radiation of an SC-cut crystal vibrator.

The Colpitts crystal oscillation circuit is a common emitter Colpitts crystal oscillation circuit where the emitter of a transistor(TR) 36 is connected to ground with a bypass capacitor for high frequencies. In this case, the bypass capacitor is replaced with a piezoelectric vibrator with a low Q. Thus, abnormal oscillation due to spurious radiation by the SC-cut crystal vibrator can be prevented and a negative resistance characteristic with a sufficiently higher resistance required to start the oscillation can be ensured.