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.