Disclosed is an alternator for a vehicle. The alternator for a vehicle according to one embodiment of the present invention includes: a brush which is in contact with a slip ring inserted into a rotor shaft of the alternator; a brush holder which includes a discharge hole opened to the lower side of the alternator to discharge carbon powder generated due to the abrasion of the brush in contact with the slip ring to the outside; and a blocking plate which is installed in the discharge hole and blocks the inflow of moisture from the outside.
