PROBLEM TO BE SOLVED: To provide an RO (Reverse Osmosis) water manufacturing apparatus eliminating a risk of contamination of an on-off valve by raw water, having a simple structure and capable of automatically washing a reverse osmosis membrane with soft water of improved water quality during supply of the RO water to a medical apparatus, and to provide a method for manufacturing the RO water using the apparatus.SOLUTION: An RO water manufacturing apparatus for supplying RO water to a medical apparatus: improves water quality of stored soft water in a soft water storage container by RO water intermittently washes a reverse osmosis membrane of an RO water manufacturing member using the soft water, the water quality of which has been improved, during the supply of the RO water to the medical apparatus and, even during the washing, continuously supply the RO water stored in the RO water storage tank to the medical apparatus.
