An electromagnetic brake contains a coil seat including plural receiving holes disposed on a front end thereof to receive plural compression springs respectively and an electromagnetic coil mounted on the front end thereof; a movable friction piece fitted on the front end thereof; a brake member fixed in a front end of the friction piece and including a transmitting shaft fitted thereon; a fixed member secured on a front end of the brake member, wherein the electromagnetic coil includes a first silicon steel ring, a plurality of slots and a number of elongate grooves, and each slot includes an isolation holder fitted therein, and the isolation holder includes a recess formed on one side thereof to correspond to the groove of the first silicon steel ring, and between two abutting isolation holders is provided with a coil set formed by an enameled copper wire.