A stator core of a rotating electrical machine, in which no compressive load is applied to divided cores each having an arc shape, when the divided cores are secured into a circular form, thereby decreasing the motor loss and improving the motor efficiency. The divided cores are circularly disposed, and the divided cores each having the arc shape in section perpendicular to the axial direction of the rotary axis. In the divided cores, there are provided welded portions each of which is diagonally formed between one corner end of a connecting edge and an opposite corner end of a neighboring connecting edge, thereby providing the welded portion diagonal with respect to the axial direction. The connecting edges are in parallel to the axial direction.