The present invention provides an oxygen concentrator tank unit having a pair of nitrogen adsorption vessels to which compressed air is alternately supplied a single oxygen tank body that is connected to said pair of nitrogen adsorption vessels check valves which are interposed between said single oxygen tank and said pair of nitrogen adsorption vessels respectively, said pair of check valves allowing gas flow from said nitrogen adsorption vessels to said oxygen tank and not allowing gas flow from said oxygen tank to said nitrogen adsorption vessels and a pressure reducing valve having an oxygen outlet and being connected to said oxygen tank, wherein at least one of said pressure reducing valve and a pair of adsorption-vessel connecting tubular bodies provided with said check valves is/are directly connected to a wall of said oxygen tank body, so that the arrangement around the oxygen tank body is simplified and unitized.
