A concentrating chamber in an oxygen concentrating apparatus is provided, in which a process for adsorbing nitrogen to concentrate oxygen is performed in a single case. The concentrating chamber in an oxygen concentrating apparatus includes: a casing having upper and lower openings; an adsorption unit for performing an oxygen concentration through a compressed air and counter-flowing the stored oxygen to perform a nitrogen rinsing in the casing; a check valve operating according to a predetermined pressure, for supplying the oxygen concentrated in the adsorption unit and rinsing the nitrogen adsorbed in the adsorption unit; and upper and lower manifolds for supplying the concentrated oxygen through the upper and lower ends of the casing, or supplying the compressed air and simultaneously exhausting the rinsed nitrogen, through the upper and lower ends of the casing. The concentrating chamber in an oxygen concentrating apparatus includes at least two casings.