A fan and shroud assembly includes a fan has a hub rotating around one shaft and a plurality of blades extending outwardly from the hub, a shroud encompassing the fan to adjust airflow by rotation of the fan, a guide ring portion located at a position where a predetermined gap exists between the shroud and a circumference connecting end tips of the blades so that the fan coupled to the shroud rotates, and a plurality of swirl prevention units integrally formed with the guide ring portion to prevent a motion of vortex proceeding along a circumference connecting end tips of the blades between the guide ring portion and the circumference, each swirl prevention unit having a shape in which the length of a circular arc passing each of the swirl prevention units with respect to the center of the shroud decreases as the arc is closer to the center of the shroud.