Capacitance element electrodes (E1 to E5) and a grounded reference electrode (E0) are formed on a substrate (20). At a position opposite to these electrodes (E0 to E5), a displacement electrode (40) is disposed that is Z-axially deformable as a detective member (30) is externally operated to move Z-axially. The displacement electrode (40) cooperates with the reference electrode (E0) and capacitance element electrodes (E1 to E5) to form capacitance elements (C0 to C5), respectively. Each of the capacitance elements (C1 to C5) is connected in series with the capacitance element (C0) with respect to a signal externally input. Changes in the capacitance values of the capacitance elements (C1 to C5) as the detective member (30) is moved are detected to sense the displacement of the detective member (30).