Abstract: An oxygen-enricher oxygen tank unit includes a single oxygen tank body, to which a pair of nitrogen absorption containers, which alternately receive a supply of compressed air, are connected; a check valve provided between each of the pair of nitrogen absorption containers and the oxygen tank body, wherein each check valve allows gas to flow from an associated nitrogen absorption container to the oxygen tank body, and does not allow gas to flow in a reverse direction thereto; and a pressure-reducing valve, having an oxygen outlet, which is connected to the oxygen tank body. At least one of the pressure-reducing valve and a pair of nitrogen absorption container connector-cylinders, which is provided with the check valve, is directly attached to a body-wall surface of the oxygen tank body. Hence, the structure around the oxygen tank body is simplified and unitized.