Novel Bacillus subtilis mutant strains having good productivity of various enzymes are provided through extensive analysis of strains that are derived from Bacillus subtilis via gene disruption. The Bacillus subtilis mutant strains according to the present invention have genomic structures prepared by deletion of regions listed in the columns for deficient regions. Each of these Bacillus subtilis mutant strains exerts significantly improved secretory productivity of a protein when a gene encoding such a secretory target protein is introduced so that it can be expressed, compared with a case in which the same gene is introduced into a wild-type strain.