An oxygen generator is provided to offer oxygen to a user and to control concentration of the oxygen by transferring the oxygen while discharging the oxygen through a vacuum pump. An oxygen generator includes an oxygen generating part and a dispense part. The oxygen generator includes a first adsorption bed(510) and a compressor(310). The first adsorption bed includes two adsorption beds connected with an air filter(100) in parallel. The dispense part includes a transfer pipe(830) and a vacuum pump(320). The oxygen generator more includes a first flow path(810) and a bypass flow path(840) connecting an influx unit of the vacuum pump. The bypass flow path includes a first orifice(610). A branch pipe in which a second adsorption bed(520) is installed, is branched from a second flow path(820).
