NOVELTY - A carbon monoxide selective oxidization catalyst (10) comprises platinum-containing catalyst powder (20) and co-catalyst powder (30). Component (20) contains platinum particles (22) and transition metal particles (24) supported on inorganic support (28). Component (30) contains co-catalyst particles (32) containing co-catalyst atom, supported on inorganic support (38). The co-catalyst particles does not contains platinum atom.    USE - For selectively oxidizing carbon monoxide contained in gas containing carbon monoxide and oxygen, such as reformed gas, and for carbon monoxide concentration decreasing apparatus used for polymer electrolyte fuel cell for electric vehicle. Also used for removal of carbon monoxide in sealing space such as tunnel, engine, and combustor.    ADVANTAGE - The carbon monoxide selective oxidation catalyst has excellent carbon monoxide removal capability in low-temperature region, and enables to increase durability of platinum electrode.    DETAILED DESCRIPTION - A carbon monoxide selective oxidization catalyst comprises platinum-containing catalyst powder and co-catalyst powder. The platinum-containing catalyst powder contains platinum atom-containing platinum particles and transition metal particles containing transition metal atom chosen from iron, cobalt, manganese, nickel and copper, which are supported on inorganic support (I). The co-catalyst powder contains co-catalyst particles containing co-catalyst atom chosen from cobalt, manganese, nickel and copper, supported on an inorganic support (II). The co-catalyst particles does not contains platinum atom. The catalyst is used for selectively oxidizing carbon monoxide contained in gas containing carbon monoxide and oxygen. An INDEPENDENT CLAIM is included for manufacture of carbon monoxide selective oxidization catalyst, which involves mixing platinum-containing catalyst powder and co-catalyst powder. The platinum-containing catalyst powder is obtained by supporting platinum particles and transition metal particles on inorganic support. The co-catalyst powder is obtained by supporting co-catalyst particles on inorganic support.    DESCRIPTION OF DRAWING(S) - The figure shows the model sectional drawing of carbon monoxide selective oxidation catalyst.    carbon monoxide selective oxidation catalyst (10)    platinum-containing catalyst powder (20)    platinum particles (22)    transition metal particles (24)    inorganic supports (I,II) (28,38)    co-catalyst powder (30)    co-catalyst particles (32)