Abstract: An apparatus for making oxygenated water capable of producing super oxygenated water and retaining the dissolved oxygen for long time periods, while being applicable to an open reservoir as well as a closed reservoir and having simple structure so as to be implemented in small as well as large size machines. According to an aspect of the present invention, the oxygenating apparatus circulates water contained in a water reservoir and dissolves oxygen from an oxygen source into the circulated water flow. A pump is coupled to the outlet of the water reservoir in fluid communication, and circulates the water contained in the water reservoir. An oxygen dissolving device has an inlet coupled to the pump in fluid communication and an outlet coupled to the water reservoir in fluid communication, and dissolves oxygen from the oxygen source to water supplied by the pump. A plurality of trays are installed in cascade vertically in a housing of the oxygen dissolving device.