To provide an electromagnetic engagement device capable of connecting and disconnecting the drive force certainly and provide an automatic document feeder using such an engagement device.

An energization part 64 has coil springs 641 and 642 having different energizing forces. When the magnetic attraction force of an electromagnet 61 acting on a clutch plate 62 remains small, the coil spring 642 having smaller energizing force is compressed, and the clutch plate 62 can make movement easily despite small magnetic attraction force. If the magnetic attraction force of the electromagnet 61 acting on the clutch plate 62 becomes larger, the other coil spring 641 having greater energizing force is compressed. As a result, a gear 71 and the clutch plate 62 are moved oppositely to the direction at the attracting time by the greater energizing force of the coil spring 641 when current feed to the electromagnet 61 is shut off, and the gear 71 meshing with another gear 72 can certainly be disengaged.