PURPOSE: To improve the stability of oscillation frequency of a voltage-controlled oscillation device(VCO) against changes in ambient temperature.

CONSTITUTION: In a circuit where the equivalent electrostatic capacity is varied by the oscillation frequency-controlled voltage Ec and the electrostatic capacity is generated for setting the oscillation frequency, a variable capacity element X1 to which the voltage Ec is applied in the backward bias direction with respect to the voltage Ec is connected in series to a PN junction element X2 which has the same characteristic of the terminal voltage change as the element X1 against the temperature change. So that the forward bias is secured to the voltage Ec. Then the necessary DC positive voltage is applied to the connection point between both elements X1 and X2 from a power supply Vcc via a resistance R1. Meanwhile the voltage Ec is applied to both ends of a series circuit of the elements X1 and X2.