A vehicle alternating-current power generator includes a stator formed by winding an armature winding on a stator core and a rotor arranged on the radial inside of the stator. The rotor includes a field core having a boss part and a plurality of claw-shaped magnetic pole parts, a field winding that is wound on the outer peripheral side of the boss part, and a permanent magnet that is arranged between the circumferentially adjacent claw-shaped magnetic pole parts. A d-axis magnetic circuit formed by magnetomotive force of the field winding and at least part of first and second magnet magnetic circuits formed by magnetic force of the permanent magnet are shared. When an electrical load is connected to the rotor, the relationship between a permeance Prt of the d-axis magnetic circuit and a permeance Pst of a q-axis magnetic circuit is set to satisfy Pst>Prt.