PURPOSE: To provide a voltage controller of an alternator for a vehicle having a circuit configuration which does not need a shunt resistor for detecting a current.

CONSTITUTION: Since a base potential of a transistor depends upon a collector current, the base potential of an exciting drive transistor 12 is compared with a reference voltage by an exciting current limiting reference voltage circuit 31, and the transistor 12 is turned ON, OFF. When the transistor 12 is tuned OFF, an exciting current flowing to an exciter 13 is reduced, and an output of a generator is lowered. When the transistor 12 is turned ON, the current flowing to the exciter 13 is increased, and the output of the generator is raised. This operation is repeated to control a peak value of the exciting current to a limit current value.