PURPOSE: To facilitate the circuit integration by using an oscillation active element as a temperature sensing element and a frequency control element.

CONSTITUTION: A capacitance of a depletion layer of pn junction between the base and the emitter is varied to control the oscillating frequency by varying a bias voltage fed to an oscillating active element 31 (transistor) being a component of a voltage controlled oscillator 2 and ambient temperature is obtained by detecting a base.emitter voltage. That is, the oscillating active element 31 is used for a temperature sensing element and a frequency control element. Thus, no discrete temperature sensing element and frequency control element are required and the temperature compensation crystal oscillator with circuit constitution facilitating the circuit integration is obtained.