NOVELTY - A hardly-decomposable organic compound (1) consisting of 2 elements of carbon and hydrogen, or 3 elements which added oxygen is mineralized using hydroxyl group. When hydroxyl group is present, hydroxyl group is oxidized by removing hydrogen atom and recycled. While extracting out of the system, the oxygen atom of hydroxyl group is made to double-bond. When hydrogen atom attached to carbon atom or oxygen atom is present, hydroxyl group is oxidized, recycled and extracted. With respect to unpaired electron, hydroxyl group is added continuously.    USE - Oxidative decomposition of organic compounds e.g. benzene, toluene, phenol and estradiol discharged from residual pharmaceuticals and pesticides.    ADVANTAGE - The method enables easy and reliable computation of required total number-of-moles of hydroxyl group, and additional amount of hydrogen peroxide and iron ion. Automation of computational algorithm is achieved.    DETAILED DESCRIPTION - A hardly-decomposable organic compound consisting of 2 elements of carbon and hydrogen, or 3 elements which added oxygen is used as process target and mineralized in an aqueous solution using hydroxyl group. For the target, the presence or absence of hydroxyl group is determined. When hydroxyl group is present, hydroxyl group is oxidized by removing the hydrogen atom and recycled into water. While extracting out of the system, the oxygen atom of hydroxyl group is made to double-bond. The presence or absence of hydrogen atom attached to a carbon atom or an oxygen atom is determined. When such hydrogen atom is present, hydroxyl group is oxidized by removing the hydrogen atom, recycled into water, and extracted out of the system. With respect to the unpaired electron of the carbon atom produced, or unpaired electron of oxygen atom, hydroxyl group is added continuously, and hydroxyl group is regenerated.    DESCRIPTION OF DRAWING(S) - The drawing shows a flowchart of the oxidation decomposition method of organic compounds.    Organic compound (1)    Hydrogen-peroxide addition unit (9)    Iron-ion addition unit (10)    Control apparatus (11)    Detector (12)    Computer (14)