It is configured in such a manner that a convex portion (15a) provided to an inner surface of a cover (15) protecting a rectifier device (13) and a voltage regulator (14) as components forming a vehicle AC alternator is fit in a concave portion (13a) provided to a component opposing the inner surface of the cover in close proximity and that the fitting configuration is provided to a point-symmetric position with respect to an external connection terminal (Tb or 12) of the components protruding from inside to outside of the cover.