PURPOSE: To improve accuracy, to accelerate response speed for switching, and to reduce cost, by controlling a switch driving shaft and switching a contact by expanding/contrading a piezoelectric element in voltage control.

CONSTITUTION: When a voltage is applied from a piezoelectric element 1, the piezoelectric element 1 shrinks in proportion of the voltage, and switching is made when a switch driving shaft 3 is in its form of being pressed down by the pressing force of a spring 8, and an electric contact 5 is in its form of being pushed up. At this time, a groove 7 is to be engraved in the switch driving shaft 3. Since a certain force for shifting the switch driving shaft 3 in the left direction is applied thereto, because the spring 8 presses a driving end 9 in the vertical direction. Furthermore, in order to have the switch driving shaft 3 given force from a bearing 2 all the time, contact part is cut out in a circle and sandwiched. Good accuracy, quick response, and reduced cost can be thus obtained.