Provided are a polymer which, when wetted, enables a medical apparatus for use in MRI diagnosis and therapy to be easily visible under MRI and, simultaneously, develops surface lubricity, and a medical apparatus coated with the polymer. The polymer including a copolymer composed of a substance for shortening relaxation time of a nuclear species capable of being detected by magnetic resonance, a moiety having a reactive group, and a moiety for developing lubricity is used to coat the medical apparatus, whereby excellent peel resistance, high lubricity, visibility under magnetic resonance, easy applicability, and high safety can be obtained.
