A method for manufacturing a stator, the method comprising: - a core piece stamping step of stamping, from one thin magnetic sheet, a first core piece which becomes an annular yoke portion when stacked, to compose a stator core, and a second core piece which becomes, when stacked, a tooth group formed such that both ends in a circumferential direction on an inner circumferential side of adjacent teeth (211a2) are integrally connected with each other by a thin connection portion (11a1), to compose the stator core; - a stacking step of respectively stacking the first core piece and the second core piece, to form the annular yoke portion and the tooth group; - a winding mounting step of mounting a stator winding on the tooth group; and - a press-fit step of press-fitting, in an axial direction, the annular yoke portion to an outer circumference of the tooth group on which the stator winding has been mounted, characterized in that the core piece stamping step includes: - a first stamping step of stamping a slot part in such a manner that a side surface in a circumferential direction of each slot for accommodating the stator winding is formed in a straight-line shape and an outermost-circumferential-side end of the side surface is formed to be a rounded portion; and - a second stamping step of, after the first stamping step, cutting the first core piece and the second core piece from an innermost-circumferential-side part of the rounded portion formed in the first stamping step, in such a manner that a groove (211b1) having a V shape opening toward an inner side of the stator core is formed in an inner circumferential surface of the annular yoke portion. - a core piece stamping step of stamping, from one thin magnetic sheet, a first core piece which becomes an annular yoke portion when stacked, to compose a stator core, and a second core piece which becomes, when stacked, a tooth group formed such that both ends in a circumferential direction on an inner circumferential side of adjacent teeth (211a2) are integrally connected with each other by a thin connection portion (11a1), to compose the stator core; - a stacking step of respectively stacking the first core piece and the second core piece, to form the annular yoke portion and the tooth group; - a winding mounting step of mounting a stator winding on the tooth group; and - a press-fit step of press-fitting, in an axial direction, the annular yoke portion to an outer circumference of the tooth group on which the stator winding has been mounted, - a first stamping step of stamping a slot part in such a manner that a side surface in a circumferential direction of each slot for accommodating the stator winding is formed in a straight-line shape and an outermost-circumferential-side end of the side surface is formed to be a rounded portion; and - a second stamping step of, after the first stamping step, cutting the first core piece and the second core piece from an innermost-circumferential-side part of the rounded portion formed in the first stamping step, in such a manner that a groove (211b1) having a V shape opening toward an inner side of the stator core is formed in an inner circumferential surface of the annular yoke portion.