An alternator for a vehicle includes a stator having a stator core, a stator winding having a first coil-end group and a second coil-end group on the opposite ends of the stator core The alternator further includes a rectifier disposed near the first coil-end group and an air drive unit for cooling the first and second coil-end groups. Because the first coil-end group has a larger surface to be cooled than the second coil-end group, temperature of both coil end groups is controlled so that they become equal.