Embodiments are disclosed to reliably carry out engine starting without cranking. Using an internal combustion engine 1, when an idle stop condition is established, a third path switching valve 28 that is provided at the connection of the compressed air supply path 25 and a first blow-by path 21, and a blow-by control valve 24 are "closed". The connection of the crankcase to the inlet path 14 is blocked, idling for a designated time is carried out, and finally the engine is stopped. On the other hand, when the idle stop release condition is established, an inlet valve 8 is "opened", and the first to third path switching valves 26 to 28 are "closed", thereby operating a compressor 17 for a designated period of time. Compressed air is thereby supplied to the combustion chamber 2 and the crankcase via the compressed air supply path 25, allowing an increase in the internal cylinder pressure. Finally, the engine is started.