In an engine room, heat insulators are provided on the rear side in the forth and back direction of a vehicle with respect to an engine and on the front side in the forth and back direction of the vehicle with respect to a dash panel arranged on a back side of the vehicle with respect to the engine. A top flange portion is formed at a top of a first heat insulator. The top flange portion is extending in a direction obliquely upward and backward of the vehicle to guide air heated by an exhaust system from the engine in an upward direction of the vehicle. A top bent portion is formed at a top of a second heat insulator such that the top bent portion is arranged in the vicinity of the cowling panel in order to guide the heated air in an upward direction of the vehicle.