A vehicular alternator 1 is disclosed as having a stator 2 on which an armature winding 21 is wound, a rotor 3 rotatably disposed in the stator, cooling fans 32, 33 for creating cooling winds during rotation of the rotor, a front housing 41 and a rear housing 45 with which the stator and the rotor are supported and having side areas formed with cooling wind discharge windows 42, 46, and a waterproof cover 8 located over an outer peripheral sides of the housings 41, 45. The waterproof cover 8 has a plurality of ventilation apertures 81 formed at an inclined angle different from an inclined angle at which the cooling wind discharge windows are formed.