A drainage pump comprising: a housing that defines a receiving space configured to receive fluid, the housing defining: a suction port configured to introduce fluid into the receiving space, and a first discharge port and a second discharge port that are configured to discharge the fluid in the receiving space to an outside of the housing; an impeller disposed in the receiving space and configured to rotate about a rotation axis to thereby discharge the fluid in the receiving space through the first discharge port or the second discharge port; a first rib that protrudes from an inner circumferential surface of the housing toward a center of the receiving space and that is disposed between the first discharge port and the second discharge port; and a second rib that protrudes from the first rib toward the center of the receiving space, wherein the suction port is disposed at the center of an upper surface of the housing, wherein the impeller faces the suction port in the receiving space, and wherein the first rib is disposed radially outward of the impeller, wherein the first rib has a first thickness in a radial direction of the housing with respect to the inner circumferential surface of the housing wherein the second rib has a second thickness in the radial direction with respect to the inner surface of the first rib; wherein the second rib extends from an inner surface of the first rib to a space defined between the suction port and the impeller, wherein the second rib extends in the circumferential direction along the rounded inner surface of the first rib; characterized in that the second rib protrudes from an upper portion of the first rib in the center direction, and a lower surface of the second rib that extends from the inner surface of the first rib and faces the impeller is formed to be inclined with respect to the inner surface of the first rib. a suction port configured to introduce fluid into the receiving space, and a first discharge port and a second discharge port that are configured to discharge the fluid in the receiving space to an outside of the housing; an impeller disposed in the receiving space and configured to rotate about a rotation axis to thereby discharge the fluid in the receiving space through the first discharge port or the second discharge port; a first rib that protrudes from an inner circumferential surface of the housing toward a center of the receiving space and that is disposed between the first discharge port and the second discharge port; and a second rib that protrudes from the first rib toward the center of the receiving space, wherein the suction port is disposed at the center of an upper surface of the housing, wherein the impeller faces the suction port in the receiving space, and wherein the first rib is disposed radially outward of the impeller, wherein the first rib has a first thickness in a radial direction of the housing with respect to the inner circumferential surface of the housing wherein the second rib has a second thickness in the radial direction with respect to the inner surface of the first rib; wherein the second rib extends from an inner surface of the first rib to a space defined between the suction port and the impeller, wherein the second rib extends in the circumferential direction along the rounded inner surface of the first rib; characterized in that the second rib protrudes from an upper portion of the first rib in the center direction, and a lower surface of the second rib that extends from the inner surface of the first rib and faces the impeller is formed to be inclined with respect to the inner surface of the first rib.