We investigated the mechanism of polytetrafluoroethylene (PTFE) chain scission throughin situhard X-ray photoelectron spectroscopy at room temperature, 200 °C, and 230 °C. TheC–C bonds in the main chain andC–F bonds in the side chains were broken, and F desorption from the PTFE surface was observed at room temperature. The formation of CF3was also observed from the recombination of brokenC–C bonds in the main chain and detached F, which were not induced by soft X-rays. In contrast, when the PTFE substrate was irradiated with hard X-rays at 200 °C, the CF3intensity initially produced by recombination reactions decreased with irradiation time, and the photoelectron spectrum retained the original PTFE spectrum. Under these conditions, the F1s/C1s intensity ratio did not change with the irradiation time; hence, the fragment containing only CF2, the chemical composition of the original PTFE, was desorbed. When the substrate temperature was 230 °C, the CF3intensity increased in relation to that at 200 °C. This result indicated that the formation of CF3via recombination reactions of broken molecular chains is enhanced by thermal assistance. These phenomena were considered to be based on the balance between recombination and desorption by photochemical and pyrochemical reactions. These results will lead to a better understanding of the use of X-ray-irradiated fluorine resins and PTFE in potential space-based environments. This study will also promote the improvement of PTFE microfabrication methods and thin-film formation using synchrotron radiation.