PURPOSE: To compensate a temperature to transient temperature fluctuation by sealing an entire circuit into a low-heat resistant material.

CONSTITUTION: A temperature detector 1 fitted on a printed circuit board 4, temperature compensating voltage generation part 2 and voltage controlled oscillator 3 are sealed in a low-heat resistant material 5. Therefore, no air is circulated between the temperature detector 1 and the voltage controlled oscillator 3 and temperature difference can be always suppressed lower than 1°C as well. Thus, since the main body of the oscillator is sealed in the low-heat resistant material 5, the temperature can be compensated even when a transient temperature fluctuating element is present out of the temperature compensation oscillator.