To prevent the adhesion at a contact while securing the opening condition, and to prolong the service life while improving the reliability by utilizing the repulsion Coulomb electrostatic force between a cantilever beam and a contact electrode for active turn-off condition.

In the case of turning on a switch 10, switches 34, 42 of a control circuit 30 are closed, and the control voltage 32 is supplied to control electrodes 14, 18 through a computing amplifier 36 so as to supply the differential voltage. When the control voltage is increased and the differential voltage reaches the threshold value, a cantilever 16 is deformed to come into contact with a contact electrode 20 to turn on the switch 10. In the case of turning off the switch 10, the control voltage 32 is reduced to zero, and after opening the switches 34, 42, the power source voltage 44 is raised so that the control electrodes 14, 18 have the same polarity and the same electrical potential, and the Coulomb force repulsing each other is thereby generated in both the electrodes 14, 18 so as to separate a beam 16 and an electrode 20 with the force larger than the adhesive force between both the elements 16, 20. With this structure, instability due to the mechanical operation is eliminated, and the turn-off operation is secured.