Provided is an apparatus which is capable of excellently mixing exhaust gas discharged from an engine with exhaust air to thereby improve lowering of temperature of the exhaust gas and suppression of noise. The apparatus comprises: a duct provided beneath an engine and having an upper edge surrounding an exhaust air inlet; an exhaust-gas pipe having an intra-duct portion extend inside the duct in a direction approximately perpendicular to a flow direction of the exhaust air; and an exhaust-gas-pipe cover provided just above the intra-duct portion to protect the intra-duct portion from oil which can drop down from above.