PROBLEM TO BE SOLVED: To provide a method for decomposing polysaccharides using aspergillus in which transcriptional control factors manR and xlnR are forcibly expressed simultaneously, and to provide a manufacturing method for soy sauce, the method having more improved compressibility by reducing viscosity of unrefined soy sauce.SOLUTION: The invention provides a method for decomposing polysaccharides using a transformant in which a manR gene or a homologous gene thereof, and a xlnR gene or a homologous gene thereof are forcibly expressed.