TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The catalyst contains copper oxide (30-80), zinc oxide (5-40), and aluminum oxide (15-40). The zinc oxide is derived from zinc atom and oxygen atom of zinc aluminate. The zinc oxide does not include zincite. The copper/zinc atomic ratio is 1 or more, and the zinc/aluminum atomic ratio is 0.1-1.5. Preferred Properties: The catalyst has a copper-oxide crystalline diameter of 150 Angstrom or less, a specific surface area of 120-200 m2/g, and a carbon-monoxide-absorption amount of 30-70 mu mol/g. The crystalline diameter of zinc-aluminum spinel is 100 Angstrom or less. Preferred Method: The catalyst is obtained by washing, drying and baking the deposit formed in a mixture of solution containing copper salt, zinc salt, and aluminum salt, and solution containing sodium hydroxide. The solutions have a pH of 7-11.5, preferably 8.5-11. The carbon-monoxide conversion method involves reducing concentration of carbon monoxide in hydrogen-containing gas consisting of carbon monoxide by water-gas shift reaction at 150-300 degrees C, using the catalyst. Hydrogen is obtained by carbon-monoxide conversion or by modifying hydrocarbon fuel (1) chosen from liquefied petroleum gas, town gas, natural gas, naphtha, kerosene, and light oil. EXAMPLE - (In g) copper nitrate trihydrate (94.4), zinc nitrate hexahydrate (37.4), and aluminum nitrate nonahydrate (110) were dissolved in water (1 L) to obtain liquid (A). Liquid (A) was and a sodium-hydroxide solution were simultaneously dripped in a container with water (300 mL) at 55 degrees C. The dropping rate of sodium-hydroxide solution was adjusted so that the pH was 9-9.5. The deposit was filtered and water-washed. The removed deposit was dried at 120 degrees C and baked at 350 degrees C for 3 hours, to obtain a catalyst. The catalyst contained (in mass%) copper oxide (55.3), zinc oxide (19.2), and aluminum oxide (25.4). The catalyst was compression-molded and pulverized. The catalyst had a specific surface area of 133 m2/g, a carbon-monoxide-absorption amount of 0.034 mu mol/g, a copper-oxide crystalline diameter of 106 Angstrom , and excellent activity and durability.