NOVELTY - The solid organic substance in organic material (1), is solubilized using alkali treatment. Solubilized substance is subjected to souring process by anaerobe, then to solid-liquid separation and the liquid component is methane-fermented. The formed digestion gas (8) is returned to souring process. The ammonia produced with an acid fermenter (3) is removed and solid component is returned to solubilized process.    USE - For anaerobic treatment of organic material (claimed) such as sewage sludge, its dehydrated cake, human waste, human waste sludge, purification tank sludge and garbage.    ADVANTAGE - The solid substance of high concentration is achieved economically with high decomposition ratio of organic material. Since the small size apparatus is used for treatment, reduction of heating expense and high digestion gas recovery, are achieved. Since volume reduction of incineration disposal or organic material is enabled, reclamation disposal is performed conventionally with high efficiency. Life prolongation of disposal site and energy saving at the time of incineration, are attained.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for anaerobic treatment apparatus of organic material. The apparatus has a solubilized tank (2) for solubilizing organic substance in the organic material by an alkali treatment, acid fermenter (3) for souring of solubilized substance by anaerobe, solid-liquid separator (4) for separating soured substance into solid and liquid components, methane fermentation tank (7) for forming a digestion gas by methane fermentation of the liquid component, and an ammonia removal unit. The removal unit removes ammonia (produced with the acid fermenter by introducing the digestion gas to acid fermenter) from the digestion gas. The apparatus has a path which returns as a path (6) which returns the solid component to the solubilized tank.    DESCRIPTION OF DRAWING(S) - The figure shows the structure of an anaerobic treatment apparatus. (Drawing includes non-English language text).    organic material (1)    solubilized tank (2)    acid fermenter (3)    solid-liquid separator (4)    path (6)    methane fermentation tank (7)    carbon dioxide-volatile organic substance absorption cell (9)    ammonia absorption cell (11)