An external cylindrical ring for use in this rotating electric machine includes a body portion and a flange, the body portion including a fastening region making internal contact with an outer circumferential surface of a stator core to be fastened to the outer circumferential surface of the stator core, and a skirt region located at a bottom surface side of a casing and having an inner diameter larger than an inner diameter of the fastening region. When the external cylindrical ring is fastened to the stator core, the deformation of the skirt region of the external cylindrical ring can be suppressed, thus enabling the dimensional accuracy of an outer surface of a cylindrical skirt region of the external cylindrical ring to fall within tolerance.