▎ 摘　　要

NOVELTY - A composite catalyst has a support comprises a conductor and a catalyst formed on the surface of the support and comprises iron oxide which involves removing contaminants without addition of an oxidizing agent and supply of energy, and used for decomposing organic compounds in water. USE - Composite catalyst used for decomposing organic compounds in water. ADVANTAGE - The composite catalyst can effectively remove contaminants. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: (1) a method for manufacturing a complex catalyst which involves providing a support comprises a conductor, preparing a solution containing an iron oxide precursor, putting the support unit, the counter electrode, and the reference electrode in the solution, and applying a voltage to the support unit and the counter electrode to form iron hydroxide on the surface of the support unit and preparing a composite catalyst for use in the decomposition of organic compounds in water by heat treating the support portion formed on the surface of iron oxide hydroxide; (2) a method for preparing a complex catalyst which comprises iron oxide precursor and conductor; and (3) a method for treating water which involves dispersing the complex catalyst, organic compounds, water and oxygen for use in the decomposition of the organic compound, reacting a composite catalyst is the organic compound and oxygen to generate reactive oxygen species and decomposing the organic compound by the active oxygen species.