Disclosed is a resin composition containing a polyvinyl alcohol resin (A) having an active hydrogen-containing functional group, and an N-amino poly(acrylamide)-based resin (B) having a (meta)acrylic acid structural unit represented by the general formula (1) below and an acrylamide structural unit represented by the general formula (2) below. This resin composition has high crosslinking rate, and enables to obtain a crosslinked product having excellent waterproof. ##STR00001## (In the formula, R represents a hydrogen or a methyl group, and X represents a hydrogen or an alkali metal.) ##STR00002##