To provide a low-priced electromagnetic tooth clutch/brake capable of generating necessary torque without enlarging diameter thereof.

This electromagnetic tooth clutch/brake is provided with a coil to be electrically connected and disconnected, a rotor arranged in a coil side and to be magnetized to form an electromagnet by electrifying the coil, an armature arranged opposite to the rotor and to be brought in contact and separated with/from the rotor by controlling electrical connection and disconnection to/from the coil, a rotor side tooth member fitted to the rotor, and an armature side tooth member fitted to the armature. Torque is generated by friction between the rotor and the armature and engagement of the rotor side tooth member with the armature side tooth member.