Provided is a mold part which does not generate periodic irregularities (scale pattern) which appear in the direction orthogonal to the drawing direction (MD) of the mold part having a surface which slides parallel to a molded article when the molded article is removed from the mold after injection molding during injection molding of a thermoplastic resin (in particular, a thermoplastic fluoropolymer), an injection molding method using the same, and a molded article in which periodic irregularities (scale pattern) (which appear in the direction orthogonal to the drawing direction (MD) of the mold part) do not appear. The mold part is used for injection molding of a thermoplastic resin, and includes a surface which slides substantially parallel to a molded article when the molded article is removed from the mold after injection molding, wherein the average tilt angle in the sliding direction (MD) is 1.5° or higher.