A structure of a soundproof cover for an engine room is mounted on a body frame at a rear side of the engine room in which an engine is mounted. The structure may include two or more piece members that are detachably coupled to each other and collectively form the soundproof cover in a panel shape. The soundproof cover is to be mounted on the body frame so that one side surface of the soundproof cover is directed toward the engine and the other side surface of the soundproof cover is directed toward an interior of a vehicle.