The main object of this research was to obtain a large amount of alkaline protease in a low-cost medium, for which purpose Bacillus sp. B21-2 was isolated from soil. The enzyme production by this strain reached the maximum level of 15,000 u/ml in a short cultivation time of 24–28 h in alkaline medium consisting of cheap materials such as soybean meal and bonito extract. The optimum pH and temperature for activity of the purified enzyme were 11.5 and 60°C respectively. The enzyme was stable up to 50°C but inactivated after 10 min at 60°C. The enzyme activity was completely inhibited by diisopropylfluorophosphate.