An electromagnetic clutch having a motor, a worm wheel rotationally driven by the motor, a rotor having an electromagnetic coil and rotatable about the same rotation axis as the worm wheel, an armature installed on the worm wheel and rotating with the rotor by being attracted to the rotor when electric power is supplied to the electromagnetic coil, a cover member for receiving the rotor and the armature, and a power supply mechanism provided between the cover member and the rotor and connected to a power source to supply electric power to the electromagnetic coil. The electric power supply mechanism has a fixed frame body fixed to the cover member and having a first power supply section into which electric power is inputted from the power source, a rotation frame body having a second power supply section that makes contact with the first power supply section to supply electric power to the electromagnetic coil and fitted in a relatively rotatable manner to the fixed frame body while being fixed to the rotor, and a plate-like electricity conduction member provided on the cover member and making contact with that part of the first power supply section which projects from the fixed frame body.