The invention is directed to an alkaline protease that has the amino acid sequence of SEQ ID NO: 2 or of an amino acid sequence having an identity of 90% or more thereto, except that one or more amino acid residues at positions selected from (a) position 6, (b) position 15, (c) position 16, (d) position 65, (e) position 66, (f) position 82, (g) position 83, (h) position 204, (i) position 319, and (j) position 337 of SEQ ID NO: 2, or at positions corresponding thereto, are substituted with certain other amino acid residues. The invention is also directed to detergent compositions and culture medium that contain the protease.