PURPOSE: To provide the voltage controlled oscillating circuit whose oscillation frequency is made proportional to the control voltage applied from a control terminal in a wide voltage range.

CONSTITUTION: This voltage controlled oscillator includes a resonance circuit part X provided with a varactor diode Cv and a negative resistance circuit part Y provided with an active element Q1 and changes the applied voltage supplied from the control terminal Vt to the varactor diode Cv to change the resonance frequency of the resonance circuit part, and a voltage dividing resistance R1 is arranged between the control terminal Vt and the anode terminal of the varactor diode Cv.