PURPOSE: To reduce the number of kinds of width of silicon steel plate and the steps of assembly by a method wherein a plurality of rectangular silicon steel plates are laminated and adhered with each other, trapezoidal cut block pieces are etching- processed at their ends in their height direction and a plurality of block pieces are arranged substantially in an annular form.

CONSTITUTION: A plurality of rectangular thin silicon steel plates 21 having a width W are laminated to make a height H of the block iron core, adhered with each other by adhesive agent to form a rectangular adhered block 31. The adhered block 31 is cut to form a trapezoidal shape along a cutting line to have an angle α with respect to a direction of width W of the silicon steel plate 21 at its height direction end surface of the adhered block 31, resulting in making a certain number of block pieces 33. The cutting part in the block piece is processed by chemicals and its burr is removed by the etching process to keep an insulation between the silicon steel plates 21. Thereafter, a plurality of block pieces 33 are arranged in substantial annular form, adhered by band or resin and fixed with each other. Thus, only one kind of width of the silicon steel plate may be applied to enable a reduction of the number of steps of assembly operation.