An alkaline protease producing microorganism was isolated from soil and identified as Pseudomonas sp. SJ-320. The optimum cultivation condition of Pseudomonas sp. SJ-320 for the production of alkaline protease was as follow; 1.0% casein, 0.2% ammonium chloride, 0.2% NaH₂PO₄, 1.0% fructose, 20℃, pH 10.0 and 140 h. The optimum pH and temperature for the enzyme activity were pH 8.0 and 50℃, respectively. The enzyme was relatively stable at pH 7.5∼8.5 and at temperature below 50℃. The activity of the partially purified enzyme was inhibited by He^(2+) and Cu^(2+) whereas Mn^(2+), Mg^(2+) and Ca^(2+) gave rather activating effects on the enzyme activity. ε-Aminocaproic acid and 2,4-dinitrophenol did not inhibit the enzyme, but p-chloromercuribenzoic acid and ethylendiaminetetraacetic acid inhibited the enzyme activity, indicating that reactive sulfhydryl group and metal ion group are required for the enzyme activity. The enzyme was resistant to various detergents, except for sodium dodecyl sulfate.