A cellulose-producing microbe isolated from soil was identified as a strain of Bacillus circulans SJ-102. Optimum incubation condition for the highest enzyme production was glucose 4.8%, skim milk 1.8%, ZnSO₄ 0.02% and pH 6.3 at 35℃ for 72hrs. The optimum physical condition for the highest crude enzyme production was pH 5.5 and 55 ℃ at 30min. of treatment, and the highest crude enzyme activity was obtained at 60 min, of treatment in rice straw. These results indicate that Bacillus circulars SJ-102 can be used for the microbial study on roughage digestion in ruminant animals.