A method for manufacturing a stator for a rotating electrical machine by placing coils in a stator core, wherein each of a plurality of teeth formed in a radial pattern in an inner periphery of an annular yoke portion in the stator core has tip-end parallel side surfaces formed in its tip end portion having a constant width in a circumferential direction, has intermediate tilted side surfaces continuous with the tip-end parallel side surfaces and formed in its portion whose width in the circumferential direction increases closer to an outer periphery, and has base-end parallel side surfaces continuous with the intermediate tilted side surfaces and formed in its base end portion having a constant width in the circumferential direction.