To provide a new method for modifying a biomedical material, especially the surface of a contact lens to be worn for a long period.

This method for covering the surface of the material comprises (a) a step for preparing the surface of the material, having a polymer brush containing a polymerization initiator group, and (b) a step for graft-polymerizing one or more kinds of different ethylenically unsaturated hydrophilic monomers or macromonomers on the polymer brushes modified by the polymerization initiator.