PURPOSE: To provide the high frequency clock circuit capable of outputting a high frequency clock while effectively preventing the penetrating of noise from the outside and the leakage of noise to the outside.

CONSTITUTION: A crystal oscillator 10 outputting a high frequency clock is mounted on and fixed to a ceramic substrate 12. Distribution factor LC noise filters 20a and 20b are serially connected to the power supply circuit and the signal circuit of this crystal oscillator 10. Thus, the noise to be penetrated from the outside in the crystal oscillator 10 through a power supply terminal 18a and the noise to be leaked to the outside through an output terminal 18b from the inside of the crystal oscillator 10 can be satisfactorily attenuated by the distribution factor LC noise filters 20a and 20b to be removed.