PURPOSE: To obtain a thin, ring magnet having a large outside diameter at low cost by arranging a plurality of magnet elements forming sections in a concentric circle to constitute a ring field magnet.

CONSTITUTION: Eight sector magnets 9a1-9a8 are used and arranged in a ring to constitute a field magnet 9 to fulfill the same function as that of one ring magnet. In this case, a magnet element forming a sector is constituted to have one concentric circular arc, of which the inside and outside diameters are in parallel with each other, and both side faces, which are symmetric with respect to the central line and in parallel with each other. Thus, a thin magnet can be obtained practically and at very low cost so that it is possible to manufacture an outer rotor pulse motor having a large outside diameter.