PURPOSE: To obtain high stroke and to permit sudden stop with no noise as well by a method wherein a plurality of coils are juxtaposed in a yoke and a driving piece is incorporated with free slide in a core body of a cylindrical magnetic material in the yoke and currents having different phase are flowed to the coils.

CONSTITUTION: A plurality of coils 2a, 2b are positioned for every partition 2 in the yoke 3 of a plunger body 1. An internal cylinder 5 is inserted in the yoke 3 and a magnetic core body 5b is positioned in the internal cylinder 5 to compose a driving piece 5. Furthermore, a stopper 6 and a returning spring 7 are engaged with the driving piece 5. AC currents are supplied to respective coils 4a, 4b by successively shifting phase and the thrust of the driving piece 5 is directed to the arrow direction by an eddy current and a moving magnetic field to increase the stroke of the driving piece 5. When the tail end of the core body 5 locates toward the left of the yoke 3, magnetic flux is rapidly decreased and stop is performed with no noise by suddenly stopping the driving piece 5.