PURPOSE: To reduce reverse exciting current required in release, not lessening but rather increasing the attracting force in the self-holding state, by arranging a permanent magnet in the upper part or lower part of an electromagnetic coil such that the permanent magnet may surround the whole of the outer peripheral surface of a guide tube.

CONSTITUTION: The magnetic flux of a permanent magnet 5 enters a moving core 7 passing through a part of a guide tube 3, which is magnetic air gap, inside the permanent magnet 5 when a solenoid is in the self-holding state, not exciting electromagnetic coil 4. The magnetic flux in the moving core 7 shunts upwards and downwards at the rate substantially corresponding to the ratio of the permeance of the magnetic air gap between the moving core 7 and a cover 1" of soft magnetic material to the permeance of the moving core 7 and a fixed core 6. The permeance of the former is extremely low comparing with that of the latter, where the magnetic air gap is substantially zero, however the magnetic air gap between the moving core 7 and the cover 1" is small. Therefore, the flux which enters the moving core 7 from the permanent magnet 5 flows mainly in the fixed core 6, and most of the magnetic flux produced by the permanent magnet 5 is utilized to the attraction of the moving core 7 and fixed core 6.