A VCO circuit includes: a control portion to which a first voltage is inputted and from which a second voltage corresponding to the first voltage is outputted; a current source portion to which the second voltage is inputted and from which a current corresponding to the second voltage is outputted; and an oscillator circuit to which the current is inputted and from which a signal with a frequency in accordance with the current is outputted. The control portion includes an adjusting circuit which changes the second voltage in conjunction with fluctuation of a power supply voltage. Accordingly, fluctuation of the frequency Fo of an output signal of the VCO circuit can be suppressed even when the power supply voltage of the VCO circuit fluctuates.