An axial fan forms an air inlet on one side and an air outlet on an opposite side along an axis of the axial fan. The axial fan includes a base, a bearing, a stator and a rotor. A central tube extends upwardly from the base. The stator is around the central tube. The bearing is received in the central tube of the base. The rotor is rotatably supported by the bearing. The rotor includes a hub, a plurality of rotary blades extending outwardly from the hub, and an annular wall surrounding the rotary blades. The annular wall connects to outer ends of the rotary blades to rotate with the rotary blades to guide airflow from the air inlet to the air outlet during rotation of the rotary blades.