An object of the present invention is to provide a uronic acid-containing glucan or a modified product thereof. The glucuronic acid-containing glucan of the present invention is a glucuronic acid-containing glucan in which a glucuronic acid residue is bound to at least one non-reducing end of a glucan, and the glucan is a branched α-1,4 glucan or a linear α-1,4 glucan. The glucuronic acid-containing glucan of the present invention can be provided by allowing α-glucan phosphorylase derived from Aquifex aeolicus VF5 to act on glucuronic acid-1-phosphate to thereby transfer a glucuronic acid residue to the non-reducing end of the receptor glucan.
