To heighten the attracting force by strengthening the magnetic force of an electromagnet to be attached to the bottom surface of a crushing machine.

An opening 20c is furnished in a part of the bottom surface 20b of a body frame 12, and an electromagnet device 30 in a cylindrical shape is accommodated fast in the opening, and the casing 31 of the electromagnet device 30 is surrounded in its whole periphery with an insulating material 37, and a mounting plate is installed protrusively on the base end face of the casing 31 and is secured to the body frame, wherein the insulating material 37 is positioned as interposed between the body frame 12 and the casing. A magnetic core material 32 to be accommodated in the casing 31 is composed of a center magnetic pole part 39 on which an electromagnetic coil 38 is wound, and a peripheral magnetic pole part 41 surrounding the center magnetic pole part 39 concentrically, and it is arranged so that the forefront magnetic pole surface 39a of the center magnetic pole part 39 consisting of either of the N-pole and S-pole has approx. the same area as the forefront magnetic pole surface 41a of the peripheral magnetic pole part 41 consisting of the other magnetic pole.