An impeller includes a fan frame, a hub, a plurality of axial blades and a plurality of wind guiding blades. The fan frame has a wind inlet, a wind outlet and an inner ring-shaped oblique surface, wherein the wind inlet is opposite to the wind outlet, and the inner ring-shaped oblique surface is formed at an inner side wall of the fan frame and adjacent to the wind inlet. The hub is disposed in the fan frame. The axial blades are connected to the inner side wall of the fan frame and the hub. The wind guiding blades protrude from the inner ring-shaped oblique surface.