To provide a water swelling polymer gel having a natural component high in water absorbing capacity and gel strength as constituent element and a foam from the same, and provide a production method of the water swelling polymer gel high in productivity and safety for a human body, and capable of easily producing in aqueous solvent.

The water swelling polymer gel and its production method are characterized by reacting the polysaccharide containing an esterified carboxylic group with the compound containing two or more α-amino groups originating from natural amino acids. Medical materials are formed from the above polymer gel, and also from the foam of the above polymer gel.