TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Metals: The transition metal is at least iron (Fe), nickel (Ni), cobalt (Co), manganese (Mn), copper (Cu), ruthenium (Ru), chromium (Cr), palladium (Pd), rhodium (Rh) and/or iridium (Ir), preferably iron.Preferred Carrier: The carrier has maximum pore diameter of 0.55-0.65 nm. The carrier is a solid acid.Preferred Molar Ratio: The molar ratio value between platinum content in solution used for supporting the platinum on the carrier and iron content in the solution used for supporting the iron on the carrier ((Pt)/(Fe)) is 1.5-7.5, most preferably 4, when the carbon monoxide selective oxidizing catalyst is manufactured.    TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Process: The carbon monoxide selective oxidizing catalyst is subjected to a reduction processing before being used in order to promote the carbon monoxide selective oxidizing reaction after the metal component is supported on the carrier. The reduction processing is performed at a temperature higher than a temperature of the hydrogen-rich gas used for the carbon monoxide selective oxidizing reaction, preferably the reduction processing is performed at 150-370degreesC. The carbon monoxide selective oxidation is performed at 130degreesC and the hydrogen-rich gas is supplied into the catalyst at a space velocity of about 22000 per hour. The hydrogen rich gas contains 5000 ppm of carbon monoxide, 25% of carbon dioxide and the oxygen content is such than the molar ratio between oxygen atoms and carbon monoxide molecules ((O)/(CO)), is 1. Carbon monoxide reduction is achieved at least 90%, preferably at least 98%. EXAMPLE - A pellet including ferrierite was prepared as catalyst carrier and soaked in a solution containing hexaamineplatinum hydroxide salt equivalent to 3% of the weight of the pellet in terms of platinum. Ion exchange of pellets between the cations of ferrierite and platinum ion in the platinum salt solution was performed so that the platinum was supported on the carrier pellet. The pellet was dried for 2 hours or more at 120degreesC in air and calcined for 1 hour at 250degreesC. The catalyst was subjected to reduction processing for 2 hours at 300degreesC in hydrogen air stream, and carbon monoxide selective oxidation catalyst was obtained. A test gas comprising 0.5% of carbon monoxide and 25% of carbon dioxide, oxygen content such that molar ratio of oxygen to carbon monoxide was 3 and remainder of hydrogen, was supplied into a reactor packed with the catalyst. The hydrogen rich gas was supplied into the catalyst at space velocity of 68000 per hour. Temperature of the gas was raised from room temperature to 300degreesC. The gas discharged from the reactor was measured for the carbon monoxide concentration. The results showed that reduction was reduced to greater extent (98%).