A gene encoding the mannanase of Bacillus subtilis WL-7, which had been isolated from Korean soybean paste, was cloned into Escherichia coli, and the gene product was purified from the culture filtrate of the recombinant E. coli. This mannanase gene, designated manA, consisted of 1,086 nucleotides, encoding a polypeptide of 362 amino acid residues. The deduced amino acid sequence was highly homologous to those of mannanases belonging to the glycosyl hydrolase family 26. The molecular mass of the purified mannanase was 38 kDa as estimated by SDS-PAGE. The enzyme had a pH optimum at 6.0 and a temperature optimum at $55^{circ}C$. The enzyme was active on locust bean gum, konjak, guar gum, and lichenan, while it did not exhibit activity towards yeast mannan, laminarin, carboxymethylcellulose, $eta$­glucan, xylan, and para-nitrophenyl-$eta$-mannopyranoside.