Provided is an AC generator for a vehicle, which is improved in heat-radiation performance and vibration resistance with a simple configuration. The AC generator for a vehicle includes a rectifier which is mounted to a rear bracket (2) and is electrically connected to a stator, for rectifying an alternating current generated in the stator into a direct current. The rear bracket (2) includes a bracket main body (30) having intake windows (32) and exhaust windows (34) partitioned by ribs (33), and a bearing housing portion (41) for housing a bearing therein, a mounting leg portion (31) extending radially outward from the bracket main body (30) so as to be mounted to a mounting target member, and an expanded portion (37) expanding radially from the mounting leg portion (31) toward a circumferential edge portion of the bracket main body (30).