To reduce an exhaust noise while keeping the air quantity of a radiator cooling fan.

A cooling fan 4 is placed in the rear of a radiator 1, and a cylindrical shroud 8 is arranged to surround the circumference of a blade part 7 connected to its driving motor 5 through a rotating shaft 6. The shroud 8 and the blade part 7 are integrated to be integrally rotatable. The shroud 8 is provided with inlet-side and outlet-side bellmouth parts 10, 11 in front and in the rear. The front end of the inlet-side bellmouth 10 is placed apart from the back face of the radiator 1 by a prescribed distance, and a full-circumferential clearance 15 is formed in the front end of the bellmouth 10 to form a space opened to the outside of the shroud 8 through the clearance 15 in front of the blade part 7, thereby reducing the noise while keeping the air quantity.