The nature of electronic interaction between noble metal and semiconducting oxide was investigated for Pd-loaded SnO2 sensor elements. It was shown that SnO2 grains contacting to PdO were strongly depleted of electrons in air. This electronic interaction disappears on exposure not only to H-2-containing air but also to He (inert gas). On the basis of these results, it was suggested that the adsorbed oxygen formed at the PdO-SnO2 interface is responsible for the electronic interaction.