An alternator can reduce the size of welding equipment and shorten the time of welding operation while ensuring high performance and high quality with the generation of electromagnetic noise being suppressed. The alternator includes a rotor having N poles and S poles alternately formed along a circumferential direction thereof, a stator core arranged so as to surround the rotor and having a plurality of axially extending slots formed at a predetermined pitch in the circumferential direction thereof, and a stator having a stator winding fitted into the slots. The stator core is formed by deforming by bending a hexahedral element iron core composed of iron core blocks with their adjacent ends being in abutment with each other and fusion bonded by welding. The weld portions of the blocks have a depth fusion extending at least up to a tensile region where a tensile stress of the stator core is generated.