Abstract: A fluoropolymer, e.g. polytetrafluoroethylene, is easily and efficiently converted into a lower molecular weight polymer in the form of a fine powder by subjecting the fluoropolymer to contact reaction with a gas comprising molecular fluorine or a suitable fluoride such as nitrogen trifluoride or xenon difluoride at a temperature between the melting temperature of the fluoropolymer and 600.degree. C., extracting a hot reaction gas produced by the contact reaction from the reactor and cooling the extracted reaction gas to a temperature not high than 100.degree. C. to thereby precipitate the molecular weight reduced fluoropolymer contained in the hot reaction gas as vapor.