A manufacturing method of a rotating electric machine includes the steps of: preparing a plurality of split stator cores annularly arranged at intervals in a circumferential direction so that their inner end portions are aligned with an imaginary circle and a support member positioned inside the imaginary circle in a radial direction to support the inner end portions of split stator cores; mounting a fastening member on outer peripheries of split stator cores to press respective split stator cores inward in the radial direction; and displacing split stator cores pressed by fastening member inward in the radial direction while the support member is supporting split stator cores.