A method for producing low molecular weight polytetrafluoroethylene less likely to generate C8-C14 perfluorocarboxylic acids and salts thereof. The method includes: (1) feeding into an airtight container: polytetrafluoroethylene; at least one additive selected from the group consisting of hydrocarbons, chlorinated hydrocarbons, alcohols, and carboxylic acids other than C8-C14 perfluorocarboxylic acids; and at least one selected from the group consisting of inert gases other than the above additive and oxygen adsorbents; and (2) irradiating the polytetrafluoroethylene to provide low molecular weight polytetrafluoroethylene having a complex viscosity of 1×102 to 7×105 Pa·s at 380° C.