Analysis is made comprehensively on gene-disrupted strains derived from Bacillus subtilis to discover a novel Bacillus subtilis mutant strain which is excellent in the ability of producing various enzymes. The Bacillus subtilis mutant strain has a genomic structure having the deletion of any one of the regions shown in the deleted region list. The Bacillus subtilis mutant strain shows a significantly improved ability of secreting and producing a desired secreted protein when a gene encoding the protein is expressably introduced into the strain, compared to a case where the gene is introduced into a wild-type strain.