To provide a method for decomposing refuse which can treat the refuse such as garbage efficiently by agitating the refuse efficiently and an apparatus for the method.

Processes are repeated, including the first process in which refuse is charged into a drum 1 to which a prescribed amount of a chip-shaped carrier supporting harmless aerobic microorganisms is supplied and in which a number of blade plates 12 are arranged on the inside surface to form a gradually spiral shape in the longitudinal direction, and while the atmosphere in the drum 1 is adjusted at a temperature, humidity, and an oxygen concentration suitable for the activity of the microorganisms, the drum 1 is rotated normally at a low speed for a prescribed time, the second process in which the drum 1 is stopped for a prescribed time, the third process in which the drum 1 is rotated reversely at a low speed for a prescribed time, and the fourth process in which the drum 1 is stopped for a prescribed time.