PURPOSE: To easily permit adjustment of the sensitivity current even in an assembled state and to allow electromagnetic devices with different sensitivity currents to be composed of the same parts by a construction wherein the resilient force of a spring acts on a movable yoke such that the free end of the movable yoke is made to depart from one of upper and lower yokes.

CONSTITUTION: When current passes through a coil 13, this current produces the magnetic flux through a path comprising an upper yoke 2, side yoke 4, lower syoke 3, fixed core 10, space including return spring 11 and a movable core 6, and a path comprising a depending piece 15 of the upper yoke 2, gap l, movable yoke 14, lower yoke 3, fixed core 10, space including return spring 11 and the movable core. The magnetic flux thus produced attracts the movable core 6 toward the fixed core 10. Prior to such attraction, the movable yoke 14 is attracted against the turning force of a spring 16 to come into contact with the depending piece 15 of the upper yoke 2. Then, when the force attracting the movable core 6 overcomes the resilient force of the return spring 11, the movable core 6 is moved downwards. Thus, since the movable core 6 is actually attracted following movement of the movable yoke 14, the movable core 6 is moved downwards with a strong attracting force.