To reduce a cost, improve a quality and improve a performance, by a method wherein bolt insertion holes with which an end bracket is fixed and magnet attaching parts by which C-type magnets are positioned are provided on the inner circumference side of a field yoke composed of layered thin electromagnetic steel plates.

C-type magnets 2 are attached between magnet attaching parts 1a provided on the inner circumference side of a field yoke 1 so as to position the C-type magnets 2 symmetrically. With this constitution, an exclusive positioning jig for attaching the C-type magnets 2 is not necessary and, further, even if the C-type magnet 2 falls off during the rotation, the motion in a center direction can be suppressed mechanically, so that an armature is protected from locking caused by the contact between the C-type magnet 2 and the armature. Bolt insertion holes 1b through which through-bolts by which an end bracket is fixed are inserted are provided near the center parts of the magnet attaching parts 1a of the field yoke 1 and used for guiding the through-bolts when a motor is assembled, and the through-bolts can be tightened easily without being attracted by the C-type magnets 2.