PURPOSE: To attain accurate temperature compensation by providing two groups of switch elements selectively subject to on/off control in response to compensation data and selecting the element of each group so as to control a load capacity of a crystal.

CONSTITUTION: Compensation data corresponding to a selected address signal are outputted from a digital memory 14. The compensation data are given to a decoder 15 and an output of the decoder applies selective on/off control to m-sets of switch elements 16. A 1st switch array 16a comprising (m-n) sets of the switch elements among the m-sets of the elements 16 connects selectively (m-n)-sets of capacitive elements 17a of the same capacitance controlling a load capacitance of a crystal vibrator 11b to the vibrator 11b. Moreover, the remaining n-sets of switch arrays 16b connect selectively n-sets of capacitive elements 17b of whose capacitance is 1/(n+1) of the capacitance of the element 17a similarly to the vibrator 11b. Then the arrays 16a, 16b control the element 17b whose capacitance is 1/(n+1) of the capacitance of the element 17a as one control step corresponding to the compensation data.