Abstract: The present invention relates to a method and an apparatus for fermentation of cattle dung or like organic waste material containing high percentage of water. In a method of accommodating a treating object material consisting of an organic waste material containing a predetermined quantity of water in a fermentor for fermentation, a method of the present invention comprises the step of granulating the treating object material in a nodular-shape before being accommodated in the fermentor for fermentation with the supply of warm air in starting of fermentation through manually communicating ventilation spaces formed between the surfaces of the adjacent granules of the treating object material. The percentage of water content in the treating object material before being granulated is controlled until a percentage of water content enough to permit granulation and aerobic fermentation is reached.