A xylanase gene xynG1 was isolated and sequenced from Aspergillus oryzae KBN616 used for making shoyu koji. The structural part of the xynG1 gene was found to be 725 bp and was predicted to be interrupted by a single intron which was 62 bp in size. The mature XynG1 was predicted to be 189 amino acids in size and had high amino acid homology to other fungal xylanases classified in family 11 glycosidase. The XynG1 was detected in the culture supernatant of A. oryzae KBN616 grown in xylan medium but was not detected when A. oryzae KBN616 was grown in glucose medium. The xynG1 gene was introduced into A. nidulans and was found to be expressed even in the glucose media. This expression pattern was confirmed using a luciferase gene as a reporter in A. nidulans.