To provide a method for adjusting control frequency characteristics of a piezoelectric oscillator by which an oscillated frequency outputted, in response to a received control voltage can be adjusted accurately into a frequency within specification.

This method for adjusting the control frequency characteristics of a piezoelectric oscillator 1, having a piezoelectric vibration element X and outputting an oscillated frequency (f), in response to a control voltage comprises a 1st adjustment step where adjusting a load capacitance connected to the piezoelectric vibrating element 1 adjusts gradation in the control frequency characteristic, a 2nd adjustment step where changing a mass of an electrode of the piezoelectric vibration element X adjusts the oscillated frequency (f) to a nominal frequency, and a seal step where the piezoelectric vibration element X in a built in state is sealed.