To provide a production method for producing a polymer member in which a pressurized fluid containing a modifying material is introduced more easily and stably into a molten resin in an injection molding machine. This task is solved by providing a production method, for producing a polymer member by using an injection molding machine provided with a mold and a heating cylinder, the method including: introducing, into a molten resin in a heating cylinder, a pressurized fluid containing a modifying material, liquid carbon dioxide, and a liquid in which the modifying material is dissolvable while controlling a flow rate of the pressurized fluid by a cylinder; and injecting the molten resin, into which the pressurized fluid is introduced, into the mold to form the polymer member in which the modifying material is contained in a surface of the polymer member.