<p>In a capacitor, the capacitance of which is changed by an externally applied DC bias, the number of stacked electrodes equipped in the capacitor main body is reduced and a voltage required for applying the DC bias is also reduced. The capacitor main body (23) is provided with a DC bias applying electrode (25), a capacitance acquiring electrode (26), and an earth electrode (24). The DC bias applying electrode (25) is positioned between the capacitance acquiring electrode (26) and the earth electrode (24). The earth electrode (24) is made to serve not only as an electrode for applying the DC bias but also as an electrode for acquiring the capacitance.</p>
