A manufacturing method of a helical core for a rotating electrical machine includes: first step forming a yoke portion extending along one direction and tooth portions protruding toward a width direction of the yoke portion from a first side edge of the width direction, with respect to a belt-shaped metal plate extending along the one direction; second step forming a notch at a position between tooth portions of the yoke portion after the first step; and third step processing the belt-shaped metal plate into a helical shape by applying bending to the metal plate so that the belt-shaped metal plate is curved toward the width direction sequentially from a portion where the notch is formed after the second step, and in the third step, a distance between a position where the application of bending starts and the position where the notch is formed is limited to within a predetermined dimension.