NOVELTY - The apparatus has a tank (1) that digests waste material into digested sludge. A supply unit (2a) supplies digested sludge from tank to a modifier (3). The modifier oxidizes digested sludge into modification sludge. A separator (8) separates digested sludge into thickened sludge and liquid. The sludge return units (7,9) return portion of modification and thickened sludge to tank. A heating unit (6) of modifier utilizes bivalent iron compound precipitated in the digested sludge by adding hydrogen peroxide at certain temperature condition for performing an oxidation process.    USE - Apparatus for processing organic-waste material such as livestock excretion, sewage sludge, surplus sludge of industrial-waste-water and plant residue for recovering methane gas.    ADVANTAGE - The huge amount of methane gas can be recovered effectively from organic solid substance. The usage-amount of chemical solution can be reduced. The quantity of organic solid waste can be reduced. The usage-cost of chemical solution can be reduced. The removal efficiency of nutrient salt in separated liquid can be improved. The spilling of phosphate and carbonate to separated liquid can be prevented. The reformation sludge can be biodegraded easily. The conversion ratio of waste material into methane gas can be improved. The requirement of acid can be prevented. The productivity of organic-waste processing apparatus can be improved. The methane can be fermented smoothly. The ultimate disposal of methane-fermented modification sludge can be performed. The usage property of resources can be improved. The phosphorus resources can be recycled efficiently.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for an organic-waste processing method.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the processing apparatus. (Drawing includes non-English language text)    Tank (1)    Supply unit (2a)    Modifier (3)    Heating unit (6)    Sludge return unit (7,9)    Separator (8)