To reduce noise, there is provided an alternator for motor vehicles having a rotor and a stator which is mounted between a pair of brackets. In the alternator a stator core forming the stator is made up of laminations of thin sheets. And at least a part of the thin sheets making up the stator core are split into four divisions or more in the circumferential direction; the thin sheets of each layer being laid with splits thereof arranged alternately in the circumferential direction.