An electric motor is provided. The electric motor includes a hollow-shaped stator configured to have a teeth part protruding on an inner surface thereof, and a rotor configured to be inserted into the hollow-shaped rotor, and including an outer surface facing the teeth part, and a plurality of poles therein. The rotor includes a bridge part disposed between poles and has a front rotor groove and a back rotor groove that are each dented at a front and a back of the bridge part with respect to a rotating direction of the rotor.