To provide a fluororesin which has a low friction coefficient, is excellent in wear resistance and exerts excellent friction characteristics in the presence of a lubricant or a hydraulic oil, a modification method of the fluororesin, a sliding member and a sliding apparatus.

The fluororesin has a structure wherein hydrogen atoms and/or fluorine atoms bonded to a carbon atom of a main backbone resin are partially substituted by oxygen-containing functional groups. The fluororesin shows an increased transmittance of visible light at a wavelength of 600 nm compared to that of the main backbone resin. The modification method of the fluororesin comprises a step wherein the hydrogen atoms and/or fluorine atoms bonded to the carbon atom of the main backbone resin are partially withdrawn to introduce unsaturated bonds and a step wherein dissociation energy of the unsaturated bonds is applied in the presence of oxygen. The sliding member and the sliding apparatus contain the fluororesin at their sliding sites.