An automotive alternator includes a rotor fixed to a shaft rotatably supported in a case, and a stator provided with a cylindrical stator core supported in the case so as to envelop the rotor, slots extending axially being formed in the stator core so as to line up in a circumferential direction at a ratio of two per phase per pole, and a stator winding constructed by installing a conductor wire coated with an electrical insulator in the stator core, a relationship between a radial dimension (d) of the conductor wire coated with the electrical insulator and a circumferential width dimension (L) of the slots being 2d