PURPOSE: To provide a long-life electromagnetic clutch without an abrasive part, by providing a rotor at two axles with projected parts on a given pitch on the opposite end faces thereof, and forming a cylindrical yoke for surrounding a coil and the end face of the rotor.

CONSTITUTION: An electromagnetic clutch comprises a yoke 1 made up of a ceramic cylindrical part and each round plate for closing the end part of the cylindrical part, a coil 2 put in an inner space, and a pair of rotors 9 and 13 opposite mounted with a gap in between on the rotating axle 5 and 6, which are put through the round plate and supported with bearings 7 and 8. The rotors 9 and 13 are made of magnetic substance. The end faces of the rotors 9 and 13 are provided in an opposite cylindrical configuration with a gap in between in the axial direction, and the opposite faces thereof have each projected part on the same pitch. Consequently, one rotor and the other rotor are joined through electromagnetic force without a mechanical abrasive contact part, and the electromagnetic clutch with a long life can be obtained.