An electric motor including a rotor including magnetic pole units and a stator including slots facing an outer peripheral surface of the rotor. Each of the magnetic pole units is bulged to an outside in a radial direction so that a waveform of a magnetic flux density generated from the rotor is a sine wave shape, and a concave part or convex part which is small enough to prevent changing of a waveform cycle of cogging torque determined by a least common multiple of the number of slots and the number of magnetic poles of the rotor, is formed at a central part in a circumferential direction of an outer peripheral surface in each of the magnetic pole units.