To provide a method for increasing efficacy and digestibility of saccharide contained in a ligunocellulosic material, by expanding the cellulosic material.

This method comprises contacting the ligunocellulosic material with liquid ammonia with which the ligunocellulosic material is impregnated, and then subjecting the liquid ammonia to gas expansion by suddenly reducing pressure, so as to expand the ligunocellulosic material. The cellulosic material is continuously treated by using an apparatus which has a screw in its barrel. A temperature of the barrel is 30 to 100°C. Corn fodder or straw is used as the ligunocellulosic material. The ligunocellulose is ground to have a length of 0.01-1.0 inch, and further contains water in an amount of 10% to 80% based on a dry weight of the ligunocellulosic material, before it is introduced into a feed slot of the screw in the barrel of the apparatus.