PURPOSE: To remove deterioration in electrical characteristics and variation in dimensional accuracy and make a proper arrangement unnecessary after press-cutting by forming separable salient pieces in each iron plate to be laminat ed and by binding said salient pieces to each other before laminating the iron plate.

CONSTITUTION: An iron core 20 is formed by lamination of a plurality of annular iron plates 21. On the outer peripheral face of this iron plate 21, arrowhead- like salient pieces 25 are formed at intervals of 90 degrees. The iron-plate side end of each salient piece 25 is formed so as to taper to a sharp point and is connected with the iron plate 21. Therefore, this end forms a boundary where the salient piece 25 is separated from the iron plate 21. Then, the iron plates 21 are piled up so that tees 23 and slots 24 are arranged properly, and caulking projections 26 of piled salient pieces 25 are caulked for lamination of the iron plate. In this state, insulation coating is applied to the iron plate which is further provided with a winding. After that, the salient piece 25 is folded and then separated from the iron plate 21.