To study the possibility of agricultural utilization of sewage sludge, the changes of the substances physico-chemical and microbiological properties composting periods such as inorganic matter, the form of organic matter and nitrogen and the kinds and the population number of microorganisms were investigated. The results were summarized as follows ; Temperature and $CO_2$ generation, they were the highest in the second day of composting periods and then were gradually fallen. pH value was not changed in first day during composting periods, but in second day was rapidly increased and then it was constant of the range of 8.4∼8.6. The contents of $P_2O,;K_2O$, CaO and Fe were a little increased during composting periods, while that of ${SO_4}^{2-}$and Mn were big increased with 253${sim}$331% and 191${sim}$208% in late composting periods in comparing with early composting periods, respectively. The contents of ether extracted materials, water soluble polysaccharides, hemicellulose and cellulose were decreased but that of resins and lignin were not changed during composting periods. The contents of total and organic nitrogen during composting periods were decreased with 15${sim}$20% and 22${sim}$35%, respectively, while that of inorganic nitrogen was decreased with 75${sim}$116%. The population numbers of microorganism during composting periods was much too changed according to the kinds of microorganism and composting periods.