A polypeptide of N-acetylglucosamine-6-O-sulfotransferase and a DNA encoding the peptide are provided. The polypeptide is (a) or (b) below: (a) a polypeptide consisting of an amino acid sequence represented by SEQ ID NO: 2; or (b) a polypeptide which comprises an amino acid sequence including substitution, deletion, insertion or transposition of one or few amino acids in the amino acid sequence of (a) and which has an enzymatic activity to transfer a sulfate group from a sulfate group donor to a hydroxyl group at 6 position of an N-acetylglucosamine residue located at a non-reducing end of an oligosaccharide represented by the formula I: GlcNAc.beta.1-3Gal.beta.1-4GlcNAc (I) wherein GlcNAc represents an N-acetylglucosamine residue, Gal represents a galactose residue, .beta.1-3 represents a .beta.1-3 glycosidic linkage, and .beta.1-4 represents a .beta.1-4 glycosidic linkage.