To provide a means preventing a situation that it is difficult to stop an engine due to suction of blow-by gas when a blow-by gas suction reduction device is provided on an industrial engine.

A flow passage change over valve V is installed in a blow-by gas duct 2 communicating from an inside of an engine main body to an intake air duct 1. Blow-by gas from the engine main body is changed over to the intake air duct 1 and an atmospheric air open duct 3 by operation of the flow passage change over valve V.