Polluted groundwater containing organic compounds, CN- and chromium (Cr3+, Cr6+) was oxidized by use of ozone combined With ultraviolet (UV) radiation. In the UV-ozone processing, hydrogen peroxide was added to improve oxidation. The advantage of this oxidation process (AOP: Advanced Oxidation Process) is that there is no production of salts which Should be removed before the treated water is reused. The treated water containing Cr6+(HCrO4-) after the oxidation process was purified by passing through a cation exchange resin column and then through an anion exchange resin column. Electric conductivity of effluent water from the anion exchange resin column was less than 20 mu S/cm. This deionized water can be used in production processes. This combined process Could be applied to reuse of polluted groundwater.