To provide an electromagnetic clutch which is a constitutional element in a clutch mechanism where a time from receiving input of a stop signal to transition to a stop state, that is, a time constant of the transition to stop action is a minimum value (instantaneous value), provided with a function which can support a clutch function and to provide a clutch method which can effectively use a clutch element formed as a roughly formed material in order to reduce manufacturing costs.

In a clutch mechanism of an electromagnetic clutch, an 'engagement teeth clutch' method is employed with radial state rack shaped or spiral rack shaped engagement teeth as a constitutional element of the clutch mechanism. And an electromagnetic clutch of the 'engagement teeth clutch' is employed with the engagement teeth of a roughly formed material molded made of a bard and abrasion resistant nonferrous material (rubber, resin or an aluminum alloy) as its constitutional element.