The atomic scale structure and its dependence on Pt concentration of a Pt-doped SnO₂ (Pt–SnO₂) thin film produced by a sputter-deposition method was investigated, which showed high-performance as a methane gas sensor. Extended X-ray absorption fine structure (EXAFS) and X-ray diffraction (XRD) analyses showed that Pt–SnO₂ has a rutile structure similar to SnO₂ crystals at less than 10 at% Pt where the Pt ion was located at the Sn position in the rutile structure. There was no evidence that Pt metal clusters were formed in the Pt–SnO₂ films. The Pt–SnO₂ structure became amorphous at greater than 11 at% Pt. We found a good correlation between the methane activity and local structure of Pt.