A power supply control apparatus for controlling an electric generator of a vehicle limits the rate of change of a power supply voltage to a predetermined variation rate range, when the change is caused by operations to control the charge condition of the vehicle battery, and controls the generated power to match the drive torque applied by the engine to the generator. When the electrical load demand changes, the generated power is controlled to limit a resultant momentary change in the power supply voltage caused by an engine response delay, while minimizing a resultant momentary amount of engine speed variation.