To protect the electromagnetic coupling from the collision of an obstacle, flown off stones or the entry of foreign matter.

The seal mechanism of the electromagnetic coupling is provided with the aim of maintaining the seal off properties extending over a long period of time in that a cover 15 to conceal the whole of the electromagnetic coupling installed between propeller shafts or the like is attached to protect from the collision of flown off stones, an obstacle or the entry of foreign matter, a rotary member of one side of the electromagnetic member is rotatively supported on the body of a car with a bearing and support member, 1st sealing means 117 is interposed between the cover and the support member on said support side and a 2nd sealing member 121 is interposed between the support member and the rotary member on one side, and a 3rd sealing means is interposed between the cover and the rotary member on the other side of the electromagnetic coupling.