To provide a process for obtaining activated polysaccharide wherein the quantity of ammonia left therein is less than 0.2% by weight.

When a polysaccharide, as a starting material, is contacted with liquid ammonia in the presence of a sufficient quantity of liquid ammonia at least to wet the surface of the polysaccharide starting material under the initial pressure higher than atmospheric pressure, and at a temperature, at lowest, more than 25°C, and when the mixture is successively released from the pressure in a manner that effective volume of the polysaccharide/liquid ammonia system increases explosively while the pressure is decreased at least 5 bar, and by means of contacting the polysaccharide/liquid ammonia system in the pressured chamber, followed by transporting this polysaccharide/liquid ammonia system into an explosion chamber which has a larger volume than the pressured chamber.