A method of manufacturing a stator in a rotating electric machine. In this method, each slot has a slot peripheral wall and a slot opening, covered with an insulation coating made of an electrical insulation material. The slot peripheral wall SW has a slot bottom wall, a pair of slot side walls opposing to each other and continuing to end portions of the slot bottom wall. The insulation coating is formed continuously from the slot bottom wall to the pair of slot side walls, and a pair of holding grooves opposing to each other is formed in the insulation coating at the vicinity of the slot opening. The groove walls of the pair of the holding grooves are formed in the insulation coating, and an electrical insulation member to close the slot opening is inserted in the pair of holding grooves and held between the pair of holding grooves.