The electromagnetic clutch includes a rotating shaft : a magnetic pole body and a rotor disposed to face each other along an axial direction of the rotating shaft ; and an armature capable of moving in a direction attachable to or detachable from the rotor along the axial direction of the rotating shaft and forming a magnetic circuit with the magnetic pole body and the rotor. A linear guide apparatus includes a side seal attached to an end of the slider in the axial direction and including a lip portion coming into sliding contact with the guide rail. Each LED light guide plate has a substrate-side protrusion which is a portion to-be-held. Collapse of a pattern formed on the substrate surface is thereby suppressed or prevented. The motor is a DC brushless motor or a limited angular torque motor.