The vehicle-generator control device for controlling an output voltage of a vehicle generator by on/off-controlling an excitation current flowing into an excitation winding of the vehicle generator, includes an excitation current detecting circuit detecting an excitation current flowing into the excitation winding, and a computation circuit having a first function of correcting the excitation current detected by the excitation current detecting circuit on the basis of a current flowing into an electrical load applied with the output voltage of the vehicle generator, and a second function of calculating an output current of the vehicle generator on the basis of the excitation current.