ELECTRIC MOTOR, AND MOTOR WITH SPEED REDUCER

PROBLEM TO BE SOLVED: To provide an electric motor capable of reducing a leakage magnetic flux between adjacent teeth after providing flange parts at each front end part of a plurality of teeth of an armature core, and thereby, improving a torque constant, and to provide a motor with a speed reducer using the same.SOLUTION: Paired flange parts 65b protruding to both sides in a circumferential direction are provided at a front end part 65c provided at the outer side in a radial direction of each tooth 65 of an armature core 61. Between the flange parts 65b opposed to each other between the teeth 65 adjacent to each other in the circumferential direction, a clearance C at least twice as large as a circumferential direction width H of a tooth main body 65a except for the flange parts 65b in the tooth 65 is formed.