An alkaline protease having the following properties; a gene encoding the same; a microorganism producing the same; and washing compositions containing the same; (i) acting over a broad pH value range of 4 to 13 and achieving, at pH 6 to 12, 80% or more the activity at the optimum pH value; (ii) when treated at 40° C. for 30 minutes, being stable over a pH value range of 6 to 11; (iii) having an isoelectric point of about 8.9 to 9.1; and (iv) having casein digesting activity that is not inhibited by oleic acid. The alkaline protease of the present invention is highly stable to various surface active agents and fatty acids, and exhibits high stability to oxidizing agents, and is therefore useful as an enzyme to be used in detergents for automatic dishwashers and laundry detergents, both containing bleaching components.