PURPOSE: To enable to correct valiance of secondary characteristic of a crystal oscillator at high accuracy by adding a counter that can set frequency dividing ratio.

CONSTITUTION: A counter 201 and a setting device 202 that sets frequency dividing ratio are added between a gate circuit 107 and a counter 103. The counter 201 counts frequency dividing signals 108 of a frequency dividing circuit 102 making output from a squaring circuit 105 a gate signal, and supplies the result to counters 103, 104. By setting frequency dividing ratio of the counter 201 by the setting device 202, fluctuation of secondary temperature coefficient of a crys- tal oscillator 101 can be absorbed by frequency dividing ratio of the counter 201. Thus, valiance of secondary characteristic of the crystal oscillator can be corrected at high accuracy.