The grain size of SnO2 (D) in the thin films prepared from SnO2 sol solution decreased with decreasing film thickness when calcined at elevated temperature (800 degrees C). Because of this notable phenomenon, the resistivity and H2S sensitivity of the films showed rather complex dependence on film thickness and calcination temperature. These characteristics could be reduced into either of two simple functions of D, depending on whether the calcination temperature was lower (400 degrees C, 600 degrees C) or higher (800 degrees C).