A chemically adsorbed film having a surface layer containing fluorine groups and a stem layer chemically bonded by siloxane bonds to a substrate is formed on the surface of a frictional portion of a machine part such as a gear or a bearing or on the surface of a game ball. An excellently self-lubricating low frictional resistance machine part or game ball thus can be obtained. A frictional portion of a gear or the like, made of SiO.sub.2 or like ceramic material, is dipped and held in a solution containing a surface active material, e.g.,CF.sub.3 (CF.sub.2).sub.7 (CH.sub.2).sub.2 SiCl.sub.3dissolved in a non-aqueous solvent. A hydrochloric acid removal reaction is brought about between SiCl groups of the material, which contains a fluorocarbon and a chlorosilane group, and hydroxyl groups numerously present on the SiO2 surface, thus forming bonds ofCF.sub.3 (CF.sub.2).sub.7 (CH.sub.2).sub.2 Si(O--).sub.3over the entire frictional portion surface. A fluorine-containing monomolecular film thus is formed, which is chemically bonded to the substrate and has a thickness of about 1.5 nm.