The Pd‐doped SnO2thin film detector for gaseous components has been developed, whose detection is based on the fact that the adsorption and desorption of gases cause the remarkable change in electrical resistivity of the semiconductor. This property of SnO2film is applicable to the preferential detector for gaseous components, especially ethanol gas. SnO2thin film was prepared on the polished ferrite substrate which SiO was precoated. Both the preparation and the precoating were done by vacuum deposition. Subsequently the oxidation for SnO2film in air was done at 500–550 °C for 30–60 min. The rise rate and fall rate of temperature were 2.5 and 1.7 °C/min, respectively. The thickness of SnO2film was about 0.3–0.35 &mgr;m.