To stably control temp. of a bacillus bed by providing a latent heat accumulation material being close to a heating means for heating the bacillus bed in an apparatus wherein a raw refuse is mixed in the bacillus bed for keeping required raw refuse decomposition bacilli and the bacillus bed is stirred while it is heated at a required temp. to perform microbiologically decomposing treatment of the raw refuse.

A rotational shaft 2 is provided in a cylindrical hollow drum-like processing tank 1 and arms 3 are radially provided on this rotational shaft 2 and a stirring blade 4 is fixed on the apex of each arms 3. A bacillus bed 6 consisting of sawdust, wood pieces, etc., so as to bury approximately the rotating shaft 2 is placed in the processing tank 1 and an electric heater 11 is provided on the lower half of the outside of this processing tank 1 so as to bring the electric heater into close contact with this processing tank 1. In addition, a latent heat accumulation material 12 made of a single salt of sodium acetate 3 hydrate with a phase changing pt. (m.p.) of 58°C and a heat of fusion of 60cal/g is fixed on the outside of the heater by storing it in a bag 13 made of a resin and bringing it into close contact with the heater. It is possible thereby to automatically absorb the local change in temp. of the bacillus bed by the latent heat accumulation material and to stably control the temp.