TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Condition: The reaction (contact) temperature for methanation of carbon monoxide is 120-200degreesC. Preferred Properties: The catalyst has specific-surface-area of 30-200 m2/g and pore volume of 0.10-0.45 ml/g. Preferred Composition: The oxide support contains cobalt oxide as essential component. The content of chlorine in catalyst is 1.0 wt.% or less of oxide support weight. Preferably, the oxide support is zirconium oxide-cerium oxide-cobalt oxide (ZrO2-CeO2-CoO), zirconium oxide-nickel oxide (ZrO2-NiO), zirconium oxide-cerium oxide (ZrO2-CeO2), zirconium oxide-cobalt oxide-nickel oxide (ZrO2-CoO-NiO), nickel oxide-cobalt oxide (NiO-CoO), cobalt oxide-cerium oxide (CoO-CeO2), nickel oxide-cobalt oxide-cerium oxide (NiO-CoO-CeO2) or zirconium oxide-nickel oxide-cobalt oxide-cerium oxide (ZrO2-NiO-CoO-CeO2). EXAMPLE - Cobalt-nitrate hexahydrate (in g) (31.07), aqueous solution of zirconyl nitrate (41.37), nickel nitrate hexahydrate (6.23) and water (492.8) were mixed, to obtain aqueous solution. The obtained aqueous solution was added to 1.224 wt.% aqueous solution of sodium hydroxide (1428.6) and mixed to obtain hydrogel. The hydrogel was then aged at 80degreesC for 2 hours, filtered, washed in warm water, dried at 120degreesC for 1 day and night, and baked at 550degreesC for 1 hour, to obtain complex oxide fine particles containing cobalt oxide, nickel oxide and zirconium oxide. The obtained complex oxide fine particles was press-molded and ground to a particle size of 20-42 meshes, to obtain support for methanation catalyst. The obtained support (50) for methanation catalyst was made to absorb 10 wt.% aqueous solution of ruthenium chloride (24.9), and dried at 120degreesC for 4 hours. Subsequently, 0.1 wt.% aqueous ammonia was dispersed, left for 1 hour, filtered, washed with warm water and dried at 120degreesC for 4 hours. Subsequently, reduction-process was carried in presence of hydrogen air flow at 350degreesC for 4 hours, to obtain catalyst for methanation. The obtained catalyst had specific-surface-area of 118 m2/g, pore volume of 0.26 ml/g, and contained zirconium (49.5 wt.%), cobalt oxide (41.9 wt.%), nickel oxide (3.8 wt.%) and chlorine (0.01 wt.%). The catalyst was filed in reaction tube, and mixed gas of carbon monoxide (0.6 volume%), carbon dioxide (20 volume%), methane (2 volume%), hydrogen (51.37 volume%) and water vapor (30.3 volume%) was made to contact the catalyst at 140degreesC. The content of concentration of carbon monoxide (CO), methane (CH4) and carbon dioxide was 10 ppm, 2.24% and 0.11%, respectively.