A bacterial strain, designated as WY22, producing extracellular chitinase was isolated from the soil around the Youngduck area, after enrichment culture in a medium containing $1{\%}$ (w/v) wet colloidal chitin as a sole carbon source. The isolate was identified as a strain of Bacillus sp. based on its morphological and physiological characteristics. It was observed that Bacillus sp. WY22 could inhibit the growth of Fusarium oxysporum with hyphal extention-inhibition assay on potato dextrose agar plate supplemented with $1{\%}$ collidal chitin. Optimum culture conditions of Bacillus sp. WY22 were examined for chitinase production in a chitin medium. High level production of chitinase was observed not only in the chitin medium but in a medium supplemented with $1{\%}$ N-glucosamine or lactose instead of chitin. The optimum concentrations of colloidal chitin and yeast extract were 3.0 and $0.5{\%}$, and the optimum culture conditions for initial pH of medium and temperature were 7.0 and $30^{circ}C$, respectively, for the production of chitinase.