To provide a crosslinked polymer obtained from a fumaric acid derivative having a phosphorylcholine-analogous group and other types of monomers, a contact lens obtained through the same process of the crosslinked polymer and having a high water content ratio suppressing adhesion and deposition of stained proteins and lipids, and to provide a method for producing the crosslinked polymer.

The crosslinked polymer is obtained by polymerizing a monomer composition containing each specified amount of a fumaric acid derivative having a phosphorylcholine-analogous group (A), a monomer having a carboxy or amide group (B), a dicarboxylic acid divinyl or diallyl compound (C) and further 5-40 wt.% of added water based on 100 wt.% of the total amount of the mixed monomers, and is characterized by having content ratio of the monomer (A) of ≥15-45 wt.% at the dried state, water content ratio of ≥50-80 wt.% at the swelled state and the tensile strength of ≥50 gf/mm2.