Provided is a method and apparatus for producing pure water in which water that has been subjected to an ultraviolet oxidation treatment performed with an ultraviolet oxidation device is brought into contact with a platinum-group metal catalyst, the method and apparatus eliminating the likelihood of the catalyst being degraded and enabling decomposition of hydrogen peroxide to be performed for a prolonged period of time in a consistent manner. Water-to-be-treated is subjected to an ultraviolet oxidation treatment performed with an ultraviolet oxidation device 2 and subsequently subjected to a hydrogen peroxide removal treatment performed with a hydrogen peroxide removal device 4 including a platinum-group metal catalyst, wherein the TOC concentration in water fed to the ultraviolet oxidation device 2 is 5 ppb or less. An anion exchange resin tower 3 is installed in a stage following the ultraviolet oxidation device 2.