To make it possible to shorten the period for fermentation and to mass produce the treated products of org. refuse, such as vegetable scrap and left-overs formable as compost.

This composite producing apparatus is composed of an agitating device 1 into which the org. refuse, such as vegetable scrap and left-overs, produced from fruit and vegetable markets, school lunch centers and the kitchens of homes, etc., and fermentation bacteria are charged and agitated, a fermentation device 25 for fermenting the org. refuse after agitation by the agitating device and a heat insulating device for fermenting the org. refuse in the fermentation device by holding the org. refuse always at the prescribed temp. The agitating device 1 is provided with a vacuum means for maintaining a vacuum state in the agitating tank 2 and a heat insulating means for maintaining always the prescribed temp.