PURPOSE: To make it possible to improve easily a frequency-temperature characteristic by providing plural temperature compensating capacitors for a crystal oscillating circuit and by switching them by a slide contact fixed to a bimetal.

CONSTITUTION: A crystal oscillating circuit consisting of phase inversional amplifying inverter 1, crystal vibrator X and capacitor CT for oscillation frequency adjustment is provided with capacitors C0∼C3 for temperature compensation. Fixed contacts 3 where capacitors C0∼C3 are connected is switched by slide contact 2 fixed to bimetal which is fixed to fixing stand 4. Bimetal 1 deforms due to change of the ambient temperature, and contact 2 is connected to contact 3 of capacitors C0∼C3 of an optimum compensation capacitor according to the ambient temperature successively according to temperature change, thus compensating the temperature of the oscillation frequency automatically. Therefore, the frequency-temperature characteristic can be improved easily.