Provided is a novel xylanase having high xylanase activity. A protein consisting of an amino acid sequence described in the following (a), (b) or (c) and having xylanase activity: (a) the amino acid sequence set forth in positions 23 to 404 of SEQ ID NO: 2; (b) an amino acid sequence having at least 90% identity to the amino acid sequence set forth in positions 23 to 404 of SEQ ID NO: 2; (c) an amino acid sequence modified from the amino acid sequence set forth in positions 23 to 404 of SEQ ID NO: 2 by deletion, insertion, substitution, or addition of one or more amino acids.