An engine compartment cover for a work machine includes left and right-hand side covers for covering the sides of an engine, and a hood for covering the top of the engine. The engine compartment cover serves to enclose the engine and demarcate an engine compartment and is capable of suppressing the noise at the operator's ear level caused by the engine operating noise passing through the engine compartment cover as far as possible, whereby the level of quietness in the operator cab can be improved. In the engine compartment cover for a work machine, the hood has a box-type structure including an exterior top plate, side plates surrounding the whole perimeter of the exterior top plate, and a bottom plate opposed to the exterior top plate, and air inlet holes are provided in the side plates only, whilst an air outlet hole is provided in the bottom plate only, in such a manner that external air is drawn into the interior of the hood via the air inlet holes and air is introduced into the engine compartment via the air outlet hole.