TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The catalyst layers contain an oxide or a composite oxide, which includes molybdenum (Mo); and the oxide carrier contains an oxide or a composite oxide, which includes titanium (Ti), zirconium (Zr), tin (Sn), tungsten (W), aluminum (Al), chromium (Cr), niobium (Nb), and/or silicon (Si). The catalyst layers contain an oxide or a composite oxide, which includes W, Sn, and/or Ru; and the oxide carrier contains an oxide or a composite oxide, which includes Mo. The catalyst layers contain molybdenum oxide (MoOx), where molar ratio x falls within 1-3; and the oxide carrier contains an oxide or a composite oxide, which includes Ti, Zr, Sn, W, A1, Cr, Nb, and/or Si. The oxide carrier contains an oxide(s) consisting titanium dioxide (TiO2), zirconium dioxide (ZrO2), tin oxide (SnO2), tungsten oxide (WO3), aluminum oxide (Al203), chromium oxide (Cr203), niobium oxide (Nb205), or silicon dioxide (SiO2). The catalyst layers contain an oxide(s) consisting ruthenium oxide (RuOx), tungsten oxide (WOx), or tin oxide (SnOx), where molar ratio x falls within 1-3; and the oxide carrier contains an oxide or a composite oxide, which includes Mo. The oxide carrier contains MoO3. Preferred Parameter: The catalyst layers have an average thickness not greater than 3, preferably 0.2-3 nm; and a melting point not less than 500 and lower than 1500degreesC. EXAMPLE - Titanium oxide fine particles (20 g) were put in pure water (3000 ml) and mixed uniformly, to prepare a uniform suspension. The suspension was stirred at reflux for 1 hour. Then, a mixed aqueous solution was prepared as an aqueous solution of a metal salt containing the main catalyst metal in 42 mg/ml, by mixing an aqueous solution of hydrogen platinum chloride (H2PtCl6) and another aqueous solution of hydrogen ruthenium chloride (H2RuCl5). These two aqueous solutions were mixed, such that the ratio of the metal contained in these two aqueous solutions was equal to the ratio of the metal contained in the main catalyst alloy. Then, mixed aqueous solution (120 ml) was added to the suspension. An aqueous solution of sodium bicarbonate (50 mg of salt/ml of water) was gradually dripped into the resultant system 20 minutes later, at 10 ml/minute, until the pH value of aqueous system was changed to 9. After dripping, the aqueous solution was left at reflux for 1 hour, filtering the aqueous solution. The precipitate was held at reflux for 30 minutes with a dilute sulfuric acid. The precipitate was filtered again. The precipitate was then washed with pure water. The precipitate thus washed was held at reflux for 30 minutes with pure water, followed by filtering the precipitate and subsequently drying the filtered precipitate at 100degreesC. The precipitate dried was put in a high purity zirconia boat and reduced at 250degreesC for 2 hours while supplying 3% hydrogen/nitrogen (H2)/(N2) gas at 100 ml/minute, then the temperature was changed back to room temperature. A catalyst precursor having platinum ruthenium (PtRu) supported on the surface of the titanium dioxide (TiO2) carrier was obtained. Next, the catalyst precursor (20 g) was put in 200 ml of an aqueous solution of a hexaammonia molybdenum oxide ((NH3)6Mo7O24) that contained molybdenum oxide (MoO2.3) (2 mg/ml). The water was evaporated, while the aqueous solution was being stirred. The residue was dried at 100degreesC. Then, the catalyst precursor was put in a high purity zirconia boat and subjected to a heat treatment at 700degreesC for 5 hours, while argon gas was being supplied at 1000 ml/minute, to obtain a supported catalyst.