PURPOSE: To provide a fermentation method capable of performing uniform aerobic fermentation of an organic waste without causing excessively moistened state or hard-dried state of the bottom sediment generated in a fixed bottom fermentation tank furnished with a fixed bottom plate for precipitating the organic waste and to provide a fermentation apparatus for performing the fermentation method.

CONSTITUTION: This fermentation method alternately performs an upward aeration to pass air upward from the bottom of the sediment of an organic waste and a downward aeration to pass air from the top toward the sedimentation bottom of the organic waste. The characteristic of the fermentation apparatus for performing the fermentation method comprises connecting a blower 4 with an aeration chamber 3 under the bottom plate 2 of the fermentation tank 1 through a channel-switching means composed of automatic valve V1 and V4 and a dust and selectively connecting the aeration chamber to the exhaustion side or the suction side of the blower by the automatic control of the channel-switching means with a timer.