Chromosomal DNA fragments of Bacillus sp. YA-14, isolated from soil as a potent $eta$-xylosidase producing bacterium, were ligated to a vector plasmid pBR322 and used to transfer Escherichia coli HB101 cells. The recombinant plasmid pYXL22 was found to enable the transformants to produce $eta$-xylosidase. pYXL22 was found to contain the 7.0 kb HindIII DNA fragment originated from the Bacillus sp. YA-14 chromosomal DNA by Southern hybridization. The optimum temperature for the reaction of $eta$-xylosidase produced by E. coli HB101 (pYXL22) was appeared at 3$0^{circ}C$. The enzyme was maintained stably up to 4$0^{circ}C$ when stored 1hr at 4$0^{circ}C$. The $eta$-xylosidase was repressed completely by 0.4% (w/v) glucose concentration in E. coli HB101 (pYXL22). The optimum concentration of xylose for the $eta$-xylosidase production in Bacillus sp. YA-14 was 0.2% (w/v).