In an electric motor, in order to simplify the structure and to remarkably improve the T/N characteristic value, yoke plates mounted on a field magnet are so shaped that the total magnetic flux of the field magnet is collectively extended to the iron core of the armature with its direction repeatedly reversed. That is, in the motor, the multi-polarization is substantially obtained by designing it in such a manner that the total magnetic flux of the field magnet is not dispersed but concentrated. Hence, in the motor, unlike a conventional motor, the field magnet is not subjected to multi-polar magnetization, and the armature side is simplified in structure, and the magnetic flux from the field magnet is maximaly utilized at all times, so that the number of magnetic poles and the effective flux .PHI. are both increased.