To obtain the subject gel having excellent durability and mechanical strength by making the gel include an amino group-containing vinyl alcohol- based polymer and a specific agent for making a material water-resistant.

This gel comprises (A) an amino group-containing vinyl alcohol- based polymer, preferably a polymer of the formula [R1 to R5 are each H or a (substitute) hydrocarbon group; A is a bifunctional hydrocarbon or a bifunctional hydrocarbon containing N, O or S; X is a monofunctional group containing amino bonded to phenyl] and (B) a agent for making a material water-resistant selected from (i) a polyfunctional epoxy compound (e.g. polyamide-epichlorohydrin, etc.), (ii) an aldehyde compound (e.g. formaldehyde, etc.), (iii) a polyfunctional isocyanate compound (e.g. tolylene diisocyanate, etc.), and (iv) a water-soluble oxidizing agent (e.g. ammonium persulfate, etc.). The blending ratio of the component A to the component B by weight is preferably 99.99/0.01 to 10/90.