Provided in the present invention is an alkaline protease wherein an amino acid residue at (a) position 65, (b) position 101, (c) position 163, (d) position 170, (e) position 171, (f) position 273, (g) position 320, (h) position 359 or (i) position 387 of SEQ. ID NO:1 or at a position corresponding thereto has been selected from the following amino acid residues: position (a): proline, position (b): asparagine, position (c): histidine, aspartic acid, phenylalanine, lysine, asparagine, serine, isoleucine, leucine, glutamine, threonine and valine, position (d): valine and leucine, position (e): alanine, glutamic acid, glycine and threonine, position (f): isoleucine, glycine and threonine, position (g): phenylalanine, valine, threonine, leucine, isoleucine and glycine, position (h): serine, leucine, valine, isoleucine and glutamine, position (i): alanine, lysine, glutamine, glutamic acid, arginine and histidine.The present invention makes it possible to efficiently produce and provide alkaline proteases having activity even in the presence of a highly concentrated fatty acid, and exhibiting excellent detergency for the removal of a complex stain containing protein, sebum and the like, and therefore being useful as an enzyme to be incorporated in a detergent.