To provide a method for fermenting an organic waste high in economic and technological stability by reusing a waste of a hollow fiber membrane and a foam of open cell as a material for a bacterium bed.

A hollow fiber membrane and/or a foam of open cell is used in a bacterium bed to be utilized in fermenting an organic waste. Further the bacterium bed is mixed with activated carbon or a bacterium bed material of a conventional technology so that the bacterium bed can deal with versatility of the organic waste. A tourmaline ore is used so as to provide the bacterium bed with deodorizing function. Pumice 7 is laid under the bacterium bed 6 in a fermenter to protect a filter 8. Air supply to the bacterium bed 6 and drain from the bacterium bed 6 are carried out the pumice 7 and the filter 8.