The effectiveness of vacuum degassing and steam treatment was examined as a means to reduce waste and increase energy recovery in the treatment of sewage sludge. Equipment using a steam ejector was constructed to apply these treatments consecutively and was able to operate continuously for more than 15 min in an experiment sucking the digestive sludge. The methane component ratio in the bio-gas generated from the treated sludge increased by 11 points. Both the removal of VTS, CODcr and BOD and the digestive efficiency also increased. Further, the use of a water ejector in combination with the steam ejector and reduction of the pressure of degassing was found to promote the solubilization of digestive sludge.