Cross-linked polymers, and

The present invention provides a polymer material for medical use has sufficient biocompatibility, and with the polymeric substrate surface to change the method of forming a biocompatible cross-linked, to impart particular surface of the substrate a protein characterized as a group of choline phosphate adsorption effect and inhibition effect of inhibiting cell adhesion. The present inventors found that a specific ratio of structural units containing phosphorylcholine copolymer unit and a hydrophobic structural unit photoreactive structure can solve the above problems, and thus completed the present invention.