A drain pump for a clothes dryer, comprising: a pump motor ; an impeller connected to a rotational shaft of the pump motor; and a housing including: a bottom surface ; a side surface that extends from an edge upwardly of the bottom surface; and a pump case recessed from the bottom surface to accommodate the impeller, wherein a suction hole through which water can be suctioned is formed at a bottom of the pump case, and wherein the impeller includes: a circular hub ; an impeller shaft that extends from a central portion of a lower surface of the hub ; and a plurality of blades that extends from an outer circumferential surface of the impeller shaft and the lower surface of the hub in a radial direction of the hub, an edge of each of the plurality of blades including a linear portion and an extension portion which is gradually rounded from an end of the linear portion toward an outer edge of the hub , and the lower surface of the hub is rounded, and the hub has a longitudinal cross section in which a thickness of the hub gradually increases from the central portion of the lower surface of the hub toward the edge of the hub , to allow the water to be guided downward while being radially discharged along the lower surface of the hub . a pump motor ; an impeller connected to a rotational shaft of the pump motor; and a housing including: a bottom surface ; a side surface that extends from an edge upwardly of the bottom surface; and a pump case recessed from the bottom surface to accommodate the impeller, wherein a suction hole through which water can be suctioned is formed at a bottom of the pump case, and a bottom surface ; a side surface that extends from an edge upwardly of the bottom surface; and a pump case recessed from the bottom surface to accommodate the impeller, wherein a suction hole through which water can be suctioned is formed at a bottom of the pump case, and wherein the impeller includes: a circular hub ; an impeller shaft that extends from a central portion of a lower surface of the hub ; and a plurality of blades that extends from an outer circumferential surface of the impeller shaft and the lower surface of the hub in a radial direction of the hub, an edge of each of the plurality of blades including a linear portion and an extension portion which is gradually rounded from an end of the linear portion toward an outer edge of the hub , and the lower surface of the hub is rounded, and the hub has a longitudinal cross section in which a thickness of the hub gradually increases from the central portion of the lower surface of the hub toward the edge of the hub , to allow the water to be guided downward while being radially discharged along the lower surface of the hub . a circular hub ; an impeller shaft that extends from a central portion of a lower surface of the hub ; and a plurality of blades that extends from an outer circumferential surface of the impeller shaft and the lower surface of the hub in a radial direction of the hub, an edge of each of the plurality of blades including a linear portion and an extension portion which is gradually rounded from an end of the linear portion toward an outer edge of the hub , and the lower surface of the hub is rounded, and the hub has a longitudinal cross section in which a thickness of the hub gradually increases from the central portion of the lower surface of the hub toward the edge of the hub , to allow the water to be guided downward while being radially discharged along the lower surface of the hub . <EOS>