An alkaline protease wherein an amino acid residue at (a) position 65, (b) position 101, (c) position 163, (d) position 17-0, (e) position 171, (f) position 273, (g) position 320, (h) position 359 or (i) position 387 of SEQ. ID NO: 2 or at a position corresponding thereto has been selected from the following amino acid residues: position (a): proline, position (b): asparagine, position (e): histidine, aspartic acid, phenylalanine, lysine, asparagine, seine, isoleucine, leucine, glutamine, threonine and valine, position (d): valine and leucine, position (e): alanine, glutamic acid, glycine and threonine, position (K): isoleucine, glycine and threonine, position (g): phenylalanine, valine, threonine, leucine, isoleucine and glycine, position (h): seine, leucine, valine, isoleucine and glutamine, position (i): alanine, lysine, glutamine, glutamic acid, arginine and histidine. A method to an alkaline protease 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 useful as an ingredient in a detergent.