PURPOSE: To easily improve friction properties and abrasion properties of a plastic product by processing a surface of the molding plastic product containing a filler with an aqueous solution of an inorganic fluoride to modify the surface profile.

CONSTITUTION: A plastic product having low friction properties and abrasion resistance is obtained by processing a surface of a molding plastic product containing a filler (e.g. plastic piston) with an aqueous solution of inorganic fluoride (e.g. hydrogen fluoride and sodium fluoride), removing and modifying the filler material projected from the surface of a plastic product. The modified processing is suitably used for manufacturing a plastic piston and other plastic products such as a bearing, a rectifier, a clutch board, a gear, and a belt pulley.