Electromagnetic clutch

A compact-size electromagnetic clutch reaches a blocking state as an electromagnetic solenoid is switched from a non-driving state to a driving state and can save wasteful consumption of energy under this blocking state. This electromagnetic clutch includes a wrap spring in pressure-contact with an outer face of a cylindrical portion of a drive pulley provided on the center side thereof. One end of the wrap spring is coupled to a drive arm of a drive member operably connected to a shaft. The other end of the wrap spring is coupled to an operational member rotatable relative to the shaft and movable along the rotational axis thereof. An electromagnetic solenoid attracts the operational member. An operational mechanism permits realization of the blocking state by preventing rotation of the drive member after a twisting operation of the wrap spring subsequent to the attraction of the operational member by this electromagnetic solenoid.