To efficiently ferment org. waste in a waste fermenting device by supplying air to the whole org. waste at all times.

This waste fermenting device is provided with a storage tank 10, a rotating shaft 21 vertically extended in the tank 10 and rotated by a driving device 30 and plural agitating members 22 fixed to the different heights of the rotating shaft 21, proceeding in the tank 10 as the shaft 21 is rotated and agitating the waste M in the tank 10. A hollow part communicating with the inside of the tank 10 through its openings 22b2 is formed in each agitating member 22, and a blower 24 is furnished to send air to the respective hollow parts of the plural agitating members 22 through an air feed pipe 23 in the shaft 21. Further, the more openings 22b2 are provided to the lower agitating members 22, and the openings 22b2 are furnished on the opposite side and on the lower side in the proceeding direction of the agitating members 22.