To provide a frequency controller capable of detecting and correcting the frequency change of a voltage controlled type temperature compensated crystal oscillator (VC-TCXO) with time.

This method is provided with a temperature detecting circuit 20 for changing a temperature to an electric signal, analog/digital(A/D) converter(ADC) 21 for converting the output of the temperature detecting circuit 20 to a deal signal, D/A converter(DAC) 17 for generating a voltage to be applied to the voltage control terminal a VC-TCXO 8, arithmetic unit 12 for calculating a setting value optimum for the DAC 17 based on the output of the ADC 21 and storage device 13 reloadable for holding the setting value of the DAC 17 corresponding to the ADC 12 and the control voltage correcting value of the VC-TCXO 8 can be calculated and stored by each temperature.