β-Mannanase catalyzes endo-wise hydrolysis of the backbone of mannan and heteromannan, which are abun-dant in the cell wall structure of ungerminated leguminous seeds. The mature β-mannanase originated from Bacillus subtilis was expressed in Pichia pastoris, a methylotrophic yeast, using the leader peptide sequence of Saccharomyces cerevisiae α-factor. The cultivation of β-mannanase express-ing Pichiapastoris yields up to 1.8 g/L protein. In the super-natant the activity of the 40 kDa-total mannanase attained a level of 1102.0 IU/mL. The properties of the β-mannanase were characterized. Optimum pH and temperature for the recombinant enzyme were 5.5 and 50℃ respectively. The enzyme was stable at pH 5.0-10.0 and maintained over 30% original activity after incubating at 70℃ for 30 min.