Ultrapure water is generally produced through the oxidative decomposition of organic substances by UV irradiation (UV oxidation), deionization by ion exchange resin, and particle removal by ultrafiltration. The UV oxidation process has large energy consumption and low energy efficiency for reducing the concentration of total organic carbon (TOC) to less than 1μg/L. In addition, small amount of hydrogen peroxide is generated from water as a by-product through the UV irradiation. A photocatalysis technology was applied for a UV oxidation apparatus, but the energy efficiency was not particularly improved. Hydrogen peroxide concentration in ultrapure water was reduced to less than 1 g/L by treatment of a newly produced ion exchange resin supporting a metal catalyst for hydrogen peroxide decomposition.