PURPOSE: To perform variable control of an attractive operation speed of a plunger, by disposing an electrostriction element whose shape is displaced by application of a voltage so that a brake member contacts with a peripheral plane of the plunger.

CONSTITUTION: An electrostrictive element 10 is made of lamination-type ceramics. It is expanded/displaced in the direction of lamination by application of a voltage. The amount of expansion displacement is varied in proportion to the applied voltage value. When a voltage is applied to the electrostrictive element 10 on the attractive operation of a plunger 3 so as to displace its shape, a brake shoe 9 is pressed in contact with a peripheral plane of the plunger 3 to provide the plunger 3 with damping force. This pressing/damping force is applied in proportion to the applied voltage value. When the damping force is selected accordingly, the attractive operation of the plunger 3 is slowed, and the plunger 3 can be variably controlled and stopped.