PURPOSE: To increase the attractive force of a solenoid, by a method wherein a projection or a recess is formed on either an iron piece or a core, a recess or a projection is formed on either a core or an iron piece opposed thereto, and distance between the iron piece and the core is reduced.

CONSTITUTION: A solenoid 1 has a coil 3 comprising a lead wire wound around a core 2. Lower surface of the core 2 of the solenoid 1 is fixed to base part of an angle frame 4. An iron piece 5 is provided on position opposed to upper surface of the core 2 of the solenoid 1, and notched parts 7, 7 provided at both ends of base part of the iron piece 5 are fitted to a notched recess 6 formed at top end of the frame 4. Top end of the iron piece 5 is rockable with respect to upper surface of the core 2. A spring 8 is interposed between a projection 4a extending at lateral side of base part of the frame 4 and a projection 5a of base part of the iron piece 5. Top end of a stopper 12 has a slanted surface 13a opposed to a notched part 13 of a strike plate 10 of an electric lock 11.