Disclosed is a cooling fan including a fan rotated by a motor, for forcibly circulating the air, and a fan housing having a through hole with a predetermined inside diameter so that the fan can be mounted thereon. A curvature radius of the end of the inner circumference of the through hole sucking the air is smaller than a curvature radius of the end of the inner circumference of the through hole discharging the air. As a result, the cooling fan can minimize noises in the operation.