PURPOSE: To increase the heat transfer area, to suppress the temperature rise, to reduce in size and to enhance the output by forming a plurality of cuts on the outer periphery of a stator core, laminating the core while rotating and allowing fins to protrude to the cuts to form a stator core.

CONSTITUTION: Three cuts 13 having substantially the same radius distance smaller than the outer periphery 12 and a cut 14 having larger radium distance than the cuts 13 are formed on the circular outer periphery 12 of a stator core 10 having a plurality of slots 11 at the inside, and the cuts 13, 14 and the shape having no cut are formed in a profile shape disposed perpendicularly to the rolling direction of the material of the core 10. The cores 10 are laminated while deviating in the rotating direction at each 90 degrees, and a stator iron core having fins 15 protruding at each four at the cuts 13, 14 is formed. Thus, the radiating area is increased, the temperature rise can be suppressed, the size can be reduced, and the output can be enhanced.