Disclosed are: a polymer for treating the surface of a medical device such as a contact lens to suppress the reduction in lubricity of the device even when the device is scrubbed； a medical device having the polymer on the surface so that the reduction in lubricity over time is suppressed； and a wetting agent containing the polymer. The polymer for treating the surface is a copolymer which is water-soluble and includes as constitutional units the following monomers A and B: monomer A: a monomer containing a (meth)acryloyl group and an ester or amide structure in a molecule, in which the ester or amide structure is not constituted by including a part of the (meth)acryloyl group； monomer B: a monomer containing a (meth)acrylamide group in a molecule and having a structure different from that of the monomer A.
