The present invention includes a rotor with rotor sectors arranged around a center along the peripheral direction and a bridge between adjacent rotor sectors for connecting the adjacent rotor sectors, so that when inserting a shaft in the center of the rotor, it can be readily and firmly connected thereto by thermal and pressed insertion, and in the rotor having core plates laid on one another, a skew structure may be readily attained by connecting the core plates laid sequentially shifted by a given angle in one direction to the shaft.