Abstract: An electromagnetic powder coupling device which can be used either as a brake or a clutch. In order to remove undesirable heat in the device, one attributable to Joule heat mainly emanated by field member, a rotor and a cylinder, and to other to frictional heat, especially inevitable for this kind of electromagnetic powder coupling device which is emanated by the friction between the rotor, cylinder and the magnetic powder filled in the space between the cylinder and the rotor, the coupling device incorporates a forced air draft cooling system. Two variations of cooling systems are disclosed, both of which have, in common with, at least a blower and a plurality of passages for forced draft air cooling not only to the external part but also to the inner part of the field member and the cylinder.