To provide the frequency band switching type voltage-controlled oscillator which can make oscillation signals of multiple frequency bands sufficiently large in level.

The voltage-controlled oscillator is equipped with an oscillation part 1 which can outputs oscillation signals of multiple frequency bands and a buffer part 2 which amplifies the oscillation signals from the oscillation part 1 and the buffer part 2 is equipped with a buffer transistor 17 which amplifies the oscillation signals and a reactance circuit 25 having multiple inductance means 26 and 27 and multiple electrostatic capacity means 28 and 29 shunting the output end 24 of the buffer part 2 and the ground; and the reactance circuit 25 performs parallel resonance in the multiple frequency bands outputted by the oscillation part 1 and series resonance at the intermediate frequency of the frequency bands outputted by the oscillation part, so the oscillation signals of the respective bands outputted by the oscillation part can be amplified by the buffer part 2 to sufficient level.