PURPOSE: To make it possible to act a large suction force on a plunger when a suction coil is excited by narrowerly forming the part for primary and suction coils than other parts in the plunger.

CONSTITUTION: An electric current detection device 1 is a solenoid, and composed of a coil block 11, yoke 12, plunger 13, and a return spring 14. The block 11 is one in which a primary coil 11a, secondary coil 11b, and suction coil 11c are wound to a coil bobbin 15. The plunger 13 is formed with a magnetic body, and the lower end part of the plunger 13 is narrowerly formed than other parts. This notch 13e is formed at the part corresponding to the coils 11a and 11c. When short-circuit current is flown in a main electric wiring, the plunger 13 is retracted downward only by the suction force generated in the coil 11a. Since a notch 11e is formed at the part corresponding to the coil 11c in the plunger 13, the effective action of magnetic force for the plunger 13 can be possible also when the coil 11c is excited.