A stator core of an electric rotating machine has steel sheets formed of a steel plate wound in the cylindrical shape. Each sheet has teeth disposed along the circumferential direction of the core on the inner side of the sheet, divided end portions disposed along the circumferential direction on the outer side of the sheet, slits alternately disposed with the divided end portions along the circumferential direction, and a boundary portion disposed between the group of teeth and the group of divided end portions. The teeth and the divided end portions substantially have the same constant thickness. The boundary portion has a changing thickness decreased toward the outer side.