Abstract: The present invention provides a breather apparatus for a 4-cycle engine in which oil in a blow-by gas can be separated. The engine's starter includes a kick idle gear that transmits a rider's pedal force to the crankshaft. A hollow kick idle shaft rotates together with the kick idle gear and a clutch body whereby sprayed oil mist mixed in blow-by gas is separated by centrifugal force. The hollow kick idle shaft opens up into a breather passage, with a blow-by gas intake port on one end and a blow-by gas exhaust port on the other, through which the blow-by gas flows. Only blow-by gas without oil mist is re-circulated to an air cleaner and then to the combustion chamber to be burned again with new air. The oil mist returns to the oil pan in a transmission chamber.