PURPOSE: To provide an oscillator with which a stable oscillated signal can be easily provided by accurately compensating frequency fluctuation caused by temperature.

CONSTITUTION: The temperature of a crystal oscillator 1 is detected by a temperature detection part 31 and a temperature detecting signal TX is converted into a signal DTX by an A/D converting part 32 and supplied to a control part 33. At the control part 33, correction data are read from a memory part 34 based on the signal DTX. The read data DCV are converted to an analog signal CV by a D/A converting part 35 and supplied to the cathode of a variable capacitance diode 37. Since the value of data read from the memory part 34 is reduced when the frequency of the crystal oscillator 1 is increased by the temperature, the reverse voltage of the diode 37 is reduced and the capacitance is increased. Therefore, the frequency component increased by the temperature is compensated by the frequency component decreased by the increase of the capacitance. The frequency component decreased by the temperature is compensated by the frequency component increased by the capacitance reduction of the diode 37 caused by the data of a large value. The frequency is kept constant regardlessly of the temperature.