TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Element: The other metals are element chosen from 4B group, 6A group, 7A group, and 8 group such as tin, molybdenum, tungsten, platinum, palladium, nickel, cobalt, rhodium, and rhenium. Preferred Composition: The catalyst contains 20-90 wt.% of ruthenium with respect to sum of 100 wt.% of ruthenium and other metals. The metal-oxide support is nickel oxide, cobaltous oxide, cerium oxide, and/or (complex oxide of) zirconium oxide, alumina, titanium oxide, and silica. Preferred Properties: The catalyst has carbon monoxide absorption amount of 3-20 cm3/g-catalyst. The average particle diameter of ruthenium and other metals is 0.5-5 nm. The methanation is carried out at 120-200degreesC. Preferred Process: The catalyst is made to contact with gas containing hydrogen and carbon monoxide, and methanation is carried out. EXAMPLE - Zirconyl nitrate solution (in g) (168) having zirconium oxide concentration of 42%, cerium nitrate hexahydrate (50.2) having cerium oxide concentration of 20%, cobalt nitrate hexahydrate (100.89) having cobaltous oxide concentration of 26%, and nickel nitrate hexahydrate (46.71) having nickel oxide concentration of 12%, were dissolved in water (2800) to form aqueous solution mixture. The obtained aqueous solution mixture (95.5 wt.%) and sodium hydroxide (86.51) were dissolved in water (3200) to form hydrogel slurry. The obtained hydrogel slurry was cured at 80degreesC for 2 hours, ripe hydrogel was filtered, and washed with warm water. The resulting mixture was dried at 120degreesC for one whole day and night, and baked at 550degreesC for 1 hour to form complex oxide fine particles. The obtained complex oxide fine particle was press-molded and pulverized till particle size was adjusted to 20-42 meshes to obtain support. Ruthenium chloride (1 wt.%) and palladium chloride (0.8 wt.%) was melted till metal concentration became 10 wt.% to form impregnation solution. The obtained support (50) absorbed impregnation solution (23.56), stirred for 1 hour, and dried at 120degreesC for 8 hours. Then, sodium bicarbonate was added till pH became 10-11, washed with warm water, and dried at 120degreesC for 5 hours. The resulting mixture was reduced at 400degreesC under hydrogen atmosphere to form catalyst having average particle diameter of 0.9 nm, carbon monoxide absorption amount of 12.7 cm3/g, specific surface area of 114 m2/g and pore volume of 0.21 ml/g. The obtained catalyst was used to carry out methanation reaction, and resulting gas had excellent carbon monoxide concentration, methane concentration, and carbon dioxide concentration at 120degreesC, 140degreesC and 160degreesC.