Abstract: The method of cleaning an exhaust gas containing nitrogen oxides and oxygen in an amount larger than its stoichiometric amount relative to unburned components in the exhaust gas which includes (a) disposing an exhaust gas cleaner comprising a heat-resistant, porous inorganic oxide body made of alumina or composite oxide thereof and impregnated with Ag or its oxide, in a flow path of the exhaust gas; (b) introducing a reducing agent selected from the group consisting of gaseous hydrocarbons, liquid hydrocarbons and aliphatic oxygen-containing organic compounds into the exhaust gas on the upstream side of the exhaust gas cleaner; and (c) bringing the exhaust gas into contact with the exhaust gas cleaner at a temperature of 200.degree.-600.degree. C., thereby removing the nitrogen oxides.