A method for purifying an oxygen rich exhaust gas by simultaneously removing the carbon monoxide, hydrocarbons, and nitrogen oxides contained in the exhaust gas, which comprises:
   bringing the oxygen rich exhaust gas into contact with an exhaust gas purifying catalyst comprised of (i) at least one noble metal selected from the group consisting of platinum and palladium (ii) barium, and (iii) at least one metal selected from the group consisting of alkali metals, iron, nickel, cobalt and magnesium, supported on a carrier composed of a porous substance.