PURPOSE: To obtain the titled method excellent in practicality, by mounting a process for performing the electrolytic oxidation of phenol-containing waste water, to which nickel salt and sodium chloride were added, in a pH range of 6.5W7.5.

CONSTITUTION: In the treatment of phenol-containing waste water, nickel (II) salt and sodium chloride are added to phenol-containing waste water to adjust the pH thereof to 6.5W7.5. Nickel oxide and sodium hypochlorite formed by anodic oxidation reaction due to electrolytic oxidation are reacted and phenol- containing waste water is rapidly subjected to oxidation treatment by the formed NiO2 and nascent oxygen O.