In an on-vehicle alternator, both the magnetic flux variation frequency and maximum flux density are decreased sufficiently to thereby decrease the internal iron loss and thereby realize an increase in the current generation efficiency. The on-vehicle alternator comprises a rotor wherein magnetic pole cores that are polarized by a rotor coil to alternately different polarities are circumferentially disposed on the outer periphery thereof at prescribed equi-angular intervals. A permanent magnet which is embedded within a resin-made retainer body is provided between the magnetic pole cores and has side faces, as viewed circumferentially, which are polarized respectively to the same polarities as those of adjacent respective magnetic pole cores to thereby vary the magnetic flux quantity directed toward stator coils so as to exhibit a circumferential gentle curve. A rectifier is constructed using SiC-MOS transistors so that it is conductive and operative to thereby charge a battery with the current developed in the stator coils only when the alternating current voltages generated in the stator coils have become higher than the battery voltage.