To provide a small and high-output servomotor with improved winding density by using divided cores in a stator.

A protruding part formed on one end of a yoke in the circumferential direction of each divided core comprises a first shape of outer surface in the radial direction along an annular concentric with a cylindrical shape, and a second shape of inner surface in the radial direction along a tangent line tangent to a circle concentric with the cylindrical shape. A recessed part formed on the other end comprises a first shape of outer surface and a second shape of inner surface. The protruding part on one end of each of the divided cores is jointed in the circumferential direction with the adjacent recessed part on each of the other ends so as to be fitted to each other, thereby performing circumferencial assembly. It is thus possible to reduce looseness of the fitting parts and magnetic leakage.