The present invention provides a compact, efficient and noiseless alternator for an automotive vehicle which employs a double-layer coil arrangement in a slot for eliminating coil end interference as well as improving the space factor. An automotive alternator comprises a Lundel-type core rotor with 16 poles, and a stator with toothed portions of 96 poles spaced by slots. U-shaped conductor segments are installed in the slots. One portion of the conductor is accommodated in an outer layer portion of a predetermined slot, while the other portion is accommodated in an inner layer portion of a slot phase shifted by an electric angle of 180°. In this manner, all of the slots are separated into the inner and outer layers to accommodate a plurality of conductor segments. These conductor segments are connected only at one side of the stator to form a total of twelve wavy winding coils. These twelve wavy winding coils are divided into three groups each consisting of a serial connection of four wavy windings to constitute one phase of a three-phase stator coil.