To reduce noise caused by exhausted cooling air as well as to maintain a necessary amount of cooling air of a cooling fan. A cooling fan is positioned behind a radiator. A shroud surrounds an impeller coupled to a motor and a rotating shaft. The shroud has an inlet and an outlet in the shape of a bell mouth. The bell mouth shaped inlet has its front edge spaced from the rear surface of the radiator by a clearance D, and forms a space around its front peripheral edge. A space is formed via the space, and opens around the periphery of the shroud. The ratio A:B is 1:3 to 5, preferably approximately 1:4, where A denotes a difference between maximum and minimum diameters of the bell mouth shaped outlet of the shroud, and B notes a length of the shroud.