PURPOSE: To effectively use branches produced by pruning of street tree and garden tree and thinning of forest and to efficiently treat even used active carbon of a deodorizing device of a composite-making device for composting garbage, fallen leaves, etc.

CONSTITUTION: Branches produced by pruning of street tree and garden tree and thinning of forest are ground into small pieces, made into chips, dried and baked in a casserole to give charcoal, which is used as active carbon P in a deodorizing device 3 connected to an exhaust vent 17 on the top of a fermentation tank 1 for fermenting organic waste. Reduction in adsorbing action of the active carbon P is detected by a gas concentration at an exhaust outlet 3c side of the deodorizing device 3. At a point of time when the gas concentration exceeds a given value, the active carbon P is replaced with new one, the used active carbon P taken out is added to the fermentation tank 1 and mixed with a composite material. Consequently, the active carbon P can arbitrarily or automatically be replaced, the used active carbon P to which molds are attached is returned to the fermentation tank 1, fermentation of a material; to be treated is promoted and composting is efficiently carried out.