PROBLEM TO BE SOLVED: To provide a system and method for producing nitrogen water that stably contains nitrogen in an amount larger than that of nitrogen-saturated dissolved water obtained by replacing dissolved oxygen in water with nitrogen and dissolving nitrogen to a saturated dissolved amount.SOLUTION: A nitrogen water production method includes the following steps of: filling water into a first water tank 4 which has sealability and is provided with an opening and closing valve 41 for communicating or shutting off between an internal space and the outside, and a dissolved oxygen analyzer 43； replacing dissolved oxygen with nitrogen by injecting nitrogen gas into the water in the first water tank 4 while keeping the opening and closing valve 41 in an open state, switching the open state to a closed state by the opening and closing valve 41 when the dissolved oxygen analyzer 43 detects that the dissolved oxygen has become almost zero, and further injecting the nitrogen gas for a predetermined time to obtain nitrogen-saturated dissolved water； freezing the nitrogen-saturated dissolved water taken out from the first water tank 4 to obtain nitrogen-dissolved ice； and receiving the nitrogen-dissolved ice taken out from an ice making machine 5 in a second water tank 6 and melting it into nitrogen water .SELECTED DRAWING: Figure 1【課題】水の溶存酸素を窒素に置換して窒素を飽和溶存量まで溶解させた窒素飽和溶存水よりも、さらに多くの窒素を安定に含む窒素水の製造システム及び製造方法を提供する。【解決手段】内部空間と外部とを連通又は遮断する開閉バルブ４１と溶存酸素計４３とを具備し密閉性を備えた第１水タンク４に水を充填する工程と、開閉バルブ４１を開状態としたまま第１水タンク４内の水に窒素ガスを注入することにより溶存酸素を窒素に置換する工程と、溶存酸素計４３により溶存酸素量がほぼ零となったことを検知して開閉バルブ４１を開状態から閉状態とし、さらに所定時間だけ窒素ガスを注入することにより窒素飽和溶存水とする工程と、第１水タンク４から取り出された窒素飽和溶存水を凍結させて窒素溶存氷とする工程と、製氷機５から取り出された窒素溶存氷を第２水タンク６に収容し融解させて窒素水とする工程と、を有する。【選択図】図１
