In an electric motor, three-phase coils are provided to an armature disposed between an outside field system and an inside field system, and Halbach arrays are employed in the outside field system and the inside field system. Each of the Halbach arrays is divided by a number of divisions that is any number computed by adding two to a multiple of three. Permanent magnets are arrayed such that their magnetization directions are changed in sequence by steps of an angle computed by dividing one cycle's worth of electric angle by the number of divisions. Torque ripple is thereby suppressed in the electric motor.