To provide a crystal oscillator for reducing phase noise without using a thermostatic bath, promoting miniaturization and power saving (an initial target), and securing a start characteristic and oscillation.

The crystal oscillation comprises: a resonating circuit constituted by connecting a crystal vibrator and a division capacitor; a transistor for oscillation where a base is connected to the connection point of the crystal vibrator to the division capacitor and an emitter is to the connection point of the division capacitor; an output line which is connected between the connection point of the division capacitor and the emitter via a load resistor; and a crystal resonator which is inserted to the output line. Both the crystal vibrator and the crystal resonator include temperature compensation mechanisms.