NOVELTY - Organic wastewater containing organic substance and fats and oils, is introduced into bacteria tank (10), and bacteria process is carried out with substantial nonexistence of protozoa within bacteria tank. Then, portion(s) of fats and oils in wastewater is oxidatively decomposed and converted into cohesionless bacteria, to obtain primary treatment wastewater. The organic substance in primary treatment wastewater is oxidatively decomposed, cohesionless bacteria are removed using protozoa, and subjected solid-liquid separation using sedimentation tank.    USE - Processing of organic wastewater (claimed).    ADVANTAGE - The method enables processing of organic wastewater by reducing the quantity of fat and oil to the grade in which sewer line discharge is possible without extending large-scale installation for removing fats and oils.    DETAILED DESCRIPTION - Organic wastewater containing organic substance having biochemical oxygen demand of 2000 mg/L or less, and 50-800 mg/L of fats and oils measured as normal-hexane extract, is introduced into bacteria tank, and bacteria process is carried out with substantial nonexistence of protozoa within bacteria tank. Then, portion(s) of fats and oils in wastewater is oxidatively decomposed and converted into cohesionless bacteria, to obtain primary treatment wastewater. The obtained primary treatment wastewater is introduced into fixed bed-type catalytic oxidation tank (20) or fluidized bed-type catalytic oxidation tank, organic substance in primary treatment wastewater is oxidatively decomposed, and cohesionless bacteria is removed using protozoa, to obtain secondary-treatment wastewater. The secondary-treatment wastewater is subjected to final-treatment by solid-liquid separation using sedimentation tank. The ratio of capacity of bacteria tank and fixed bed-type catalytic oxidation tank or fluidized bed-type catalytic oxidation tank is 1:1-1:10.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of apparatus used for processing organic wastewater. (Drawing includes non-English language text)    Bacteria tank (10)    Catalytic oxidation tank (20)    Fixed bed (25)    Diffusion tube (30)