In this paper, we show some results on oxygen-concentration-dependent electrical resistances of SrTiO3-based thin films and their possible new application. It is widely known that SrTiO3-based ceramics can be alternatives to ZrO2-based high-temperature oxygen sensors, which are categorized as ionic conductors operated at high temperatures, such as at 1,273 K. In contrast, our thin-film-based devices, which are operated at room temperature, could be studied from the view point of polaron theory.