punching means for punching the rolled electromagnetic sheet steel by angularly displacing the rolled electromagnetic sheet steel relative to a die set, thereby displacing the plurality of core plates having rolling directions of the electromagnetic sheet steel angularly by a machine angle determined in accordance with a predetermined number of slots or poles provided in the laminated core structure so that a phase difference of cogging torques produced by magnetic anisotropy of the core plates is substantially 180°, wherein:

the apparatus stacks the predetermined number of core plates with respective rolling directions of the electromagnetic sheet steel angularly displaced by the machine angle with respect to a reference angle so as to produce a phase difference of cogging torques by magnetic anisotropy of the core plates,

each phase α of the cogging torque is represented by (360n/s) mod {360/(ms)}×m·s, which is a value obtained by multiplying a remainder of division of an angle (360n/s) of each of slots or poles by an angle 360/(m·s) of one cycle of the cogging torque, by m·s which is the number of cycles of the cogging torque per rotation, where s is the number of slots or poles provided in the laminated core structure, and m and n are natural numbers, and

said machine angle is determined such that the phase difference of the cogging torques is substantially 180° in an approximately rectilinear relation between the phase of the cogging torque and the machine angle of the rolling direction obtained by connecting the phases at respective angles of the slots or poles.