PURPOSE: To stabilize a core-correlated position by arranging a plurality of rotor cores provided with pinholes so that said rotor cores are separated from each other, by filling a space between said rotor cores with plastic magnet molding materials to form a permanent magnet and by filling said pinholes with said molding materials.

CONSTITUTION: Two rotor cores 1 are arranged in such manner that the peaks and bottoms of pole teeth 1-1 alternately formed on their outer peripheral faces are facing to and deviating circumferentially from each other. Then, space parts between both rotor cores are filled with plastic magnet molding materials 2 to form a permanent magnet. Further, through pinholes 1-3 are formed in the yoke part of a laminated core 1' forming said rotor core 1. Then, these pinholes 1-3 are filled with said molding materials 2 simultaneously with molding of the permanent magnet. Thus, said two rotor cores 1 are mutually positioned and fixed, and fastening of said cores to a rotor 3 is conducted after the rotor cores were formed into an integral body. In this manner, a fastening work is made easier.