We investigated the development of the apparatus for high-speed decomposition of sewage sludge. The decomposition mechanism was based on thermophilic oxic process of microorganism. Effect of additional stuff on the stable operation of the apparatus was examined by use of 6 kinds of carrier stuffs. Wood chips as an additional stuff into sewage sludge made the apparatus possible to operate stably and continuously. Decomposition of sewage sludge was carried out efficiency when the weight ratio of sewage sludge to wood chips was less than 10%. The influence of rice bran on the decomposition rate has been studied. The temperature in reaction tank rose with the addition of the rice bran. The decomposition rate of sewage sludge increased with a rise in the temperature. It was clarified that the rice bran was added to the sewage sludge to accelerate the decomposition. It is clear from the measurement of carbon dioxide concentration in exhaust that the decomposition reaction reached in the maximum about 12 hours after the beginning of reaction. The CO, evolution rate increased with a rise in the temperature. Total amount of carbon discharge in the exaust agreeded with the decrease of sewage sludge.