A voltage-controlled oscillator that can achieve low phase noise while ensuring stable oscillation startup and stable oscillation maintenance even under low supply voltage conditions. The voltage-controlled oscillator includes an LC parallel resonant circuit, whose impedance varies with a control input voltage and a negative resistance circuit for introducing negative resistance into the LC parallel resonant circuit, wherein the negative resistance circuit includes at least: a first amplifier circuit, provided in parallel with the LC parallel resonant circuit and having a first pair of transistors cross-coupled via a capacitor, that achieves class-C amplifier operation by biasing the gate of each transistor in the first transistor pair with a first bias voltage; and a similarly configured second amplifier circuit that achieves class-C amplifier operation by biasing the gate of each transistor with a second bias voltage which is different from the first bias voltage.