[Problem] To provide a hydrophilic copolymer that can form a surface lubricious layer exhibiting superior lubricating property and durability (lubrication retaining property) . To also provide a hydrophilic copolymer having a good solvent solubility.[Means for Resolution] A hydrophilic copolymer containing: structural units derived from a polymerizable monomer (A) having a sulfobetaine structure； structural units derived from a polymerizable monomer (B) having at least one group selected from the group consisting of a sulfonic acid group (-SOH), a sulfuric acid group (-OSOH), a sulfurous acid group (-OSOH), and groups of salts thereof； and structural units derived from a polymerizable monomer (C) having a photoreactive group.
