A variable capacitor is provided such that it is possible to make nonlinear distortion small and use at high power handling capability, and such that a variable rate of capacitance is not influenced by a high-frequency voltage substantially. A variable capacitor is used by changing capacitance through application across electrodes of direct current voltage and high-frequency voltage. When an effective voltage value of high-frequency voltage is within a range of voltage values of direct current voltage, there is substantially no fluctuation caused by application of high-frequency voltage with respect to a change of capacitance caused by application of direct current. Since it is possible to decrease susceptibility to the high-frequency voltage of the variable capacitor, it is possible to obtain a variable capacitor such that nonlinear distortion is small and power handling capability is high.