To provide a digestive treatment method and treatment equipment for organic sludge which are capable of making organic matter load of a digesting chamber higher than heretofore and more advancing the resource recovery from the organic sludge.

The organic sludge of a high concentration of VS exceeding 2% is treated under conditions of a pH ≥10 in a hot alkali pretreating vessel 1, by which the organic matter is solubilized. The ammonia formed at this time is separated away from the liquid in a suitable ammonia remover 5 and the pretreated sludge of the lowered ammonia concentration is subjected to methane fermentation in an anaerobic digesting chamber 2. Since there is no more methane fermentation obstruction, the solubilization rate of the organic matter is raised by pretreating the sludge of the high concentration at a higher pH than heretofore and therefore the efficiency of the methane fermentation is enhanced and the discrete recovery of the methane and the ammonia which are valuable resources is made possible.