The structure and reducibility of molybdenum oxide supported on tin oxide were studied in order to explain the high activity of molybdenum oxide for the methanol oxidation. Higher reducibility was observed for the molybdenum oxide supported on SnO2 in comparison with the values for that supported on TiO2, ZrO2, and Al2O3 The Mo-O bond lengths of the determined molybdenum oxide (0.17, 0.22 nm) on SnO2 were in agreement with those on the (100) face of MoO3 which was previously reported to be active for the oxidation; in addition, this had the structure of the active polymeric species. The high activity for the methanol oxidation may be caused by the structure and the reducibility of the loaded molybdenum oxide.