To realize stable oscillation without a secular change and to facilitate frequency adjustment by using variable capacity diodes for the adjustment of the frequency of a tank circuit.

The capacity of the variable capacity diode 11 changes by voltage supplied from a low pass filter to an input terminal IN, and an oscillation frequency can be adjusted to a decided channel. At that time, the oscillation frequency of VCO is decided by the synthesized capacity of the diode 11 and a capacity 16, the synthesized capacity of the variable capacity diode 18 and a capacity 15 and the resonance frequency of the tank circuit 10 constituted by an aircore coil 14. In such a case, the resonance frequency of the tank circuit is adjusted and variance is corrected by controlling voltage applied on the diode 13 in a variable resistor 12.