An object of the present invention is to provide a novel polyvinyl alcohol-based resin excellent in viscosity stability of an aqueous solution, high-speed coatability, reactivity with a crosslinking agent and water solubility. The invention relates to a polyvinyl alcohol-based resin comprising a structural unit having a carboxyl group-containing long-chain alkyl group on a side chain, which is represented by the general formula (1): [KA 1] ##STR00001## wherein R.sup.1 and R.sup.2 each independently represents a hydrogen atom or an alkyl group, R.sup.4, R.sup.5 and R.sup.6 each independently represents a hydrogen atom or an alkyl group, R.sup.3 represents a hydrogen atom, an alkyl group or an alkali metal, and n represents a positive integer.