Three kinds of xylanases, X-C, X-I, and X-II, were separated from culture filtrate of an alkalophilic bacteria, Bocillus licheniformis OR-1. Their molecular weights were estimated to be 29, 000, 50, 000, and 34, 000, respectively. They were most active at pH 6.0-6.5, and at temperature of 5$0^{circ}C$. Mercurc ion and p-chloromercurybenzoate inhibited the xylanase activity of X-C and X-II remarkably, whereas X-I was not affected. Xylanase X-I hydrolyzed barley straw xylan liberating xylose, xylobiose, and arabinose, while X-C and X-II produced only xylobiose and xylotriose.