Abstract: A generator apparatus driven by an internal combustion engine and comprising a revolution controller to control a revolution of the internal combustion engine so as to maintain a desired value of a terminal voltage of a battery which is charged by an output of an AC generator driven by the internal combustion engine while controlling an actuator for operating a fuel supply adjuster, an engine start controller to give a start instruction from a timer circuit to start means when the battery is discharged until the terminal voltage is lowered to a set value and an engine stop controller to give a stop instruction from the timer circuit to stop means when the battery is perfectly charged by the operation of the engine until the revolution of the engine is lowered to a stop revolution thereof whereby the starting and stopping operations of the engine are controlled without undercharging and overcharging the battery.