[Problem] To provide: a water-insoluble plant fibrous material derived from soybeans that has both the functions of imparting viscosity to liquid batter and of stabilizing viscosity a method for imparting viscosity to liquid batter using said raw material and a method for stabilizing viscosity. [Solution] The provision of an agent for imparting viscosity to liquid batter was achieved by using a water-insoluble plant fibrous raw material obtained by: heating a slurry, prepared by adding water to bean curd lees, to more than 100° C. and up to 150° C. then substantially removing the water-soluble component thereof.
