PURPOSE: To prevent generation of useless noise by saving fuel for an internal combustion engine.

CONSTITUTION: A generator 2 and a load detecting power supply circuit 3 are connected to load connecting terminals t1, t2 through a changeover switch 6. A rotation detecting circuit 5 of generating an engine stop signal Es, when an internal combustion engine is stopped, is provided, and the changeover switch 6 is actuated when the engine stop signal Es is generated, to apply an output of the load detecting power supply circuit 3 between the load connecting terminals t1, t2. A device comprises a load connection detecting circuit 8 for detecting a current of flowing in a load from the load detecting power supply circuit to detect whether the load is provided or not, engine starter 9 for starting the engine when the load is detected by the load connection detecting circuit and an engine stopper 12 for stopping the engine when an output of a load detecting circuit 11 for detecting a load current of the generator is decreased to a preset value or less.