To provide a degradable cured resin having advantageous heat resistance, solvent resistance, stability as the cured resin, having excellent degradability of the backbone thereof by heating or irradiating a light and capable of being easily removed; a composition for a cured resin as a raw material for the resin; as well as a novel polyhemiacetal ester capable of being preferably utilized for the composition and method for producing the polyhemiacetal ester.

The polyhemiacetal ester of the present invention comprises a recurring unit represented by formula (1) (wherein, R1 represents a cyclohexyl group or phenyl group; R2 represents a (1-20C) hydrocarbon group; and R3 represents an alkyl (meth)acrylate group having a (1-10C) alkyl group) and has a number average molecular weight of 1,000 to 20,000. The composition for a cured resin of the present invention is characterized by containing the polyhemiacetal ester, a curing agent having in one molecule thereof, one or more polymerizable vinyl group and a heat- or photo acid-generating agent.