A functional polymer membrane, prepared by curing a composition comprising a polymerizable compound (A) represented by Formula (1) and a monofunctional polymerizable compound (B): wherein R1 represents a hydrogen atom or a methyl group; Q represents a polyol residue formed by removing m2 hydrogen atoms from hydroxyl groups of a trivalent to hexavalent polyol; L represents a divalent linking group; m1 represents 0 or 1; m2 represents an integer of from 3 to 6, and wherein the monofunctional polymerizable compound (B) is a (meth)acrylate compound, a (meth)acrylamide compound, a vinyl ether compound, an aromatic vinyl compound, an N-vinyl compound, or an allyl compound.