PURPOSE: To obtain a catalyst whose activity in removal of nitrogen oxide under coexistence of oxygen and steam is high even under large space velocity and durability is excellent at high temperature by compatibly carrying iridium and alkaline earth metal on the carrier of metallic carbide and/or metallic nitride.

CONSTITUTION: A carrier is selected from metallic carbide such as silicon carbide and titanium carbide and metallic nitride such as titanium nitride and zirconium nitride. Iridium and alkaline earth metal such as Ca and Sr are compatibly carried on the carrier. In the catalyst obtained by such a way, higher NOx conversion and high-temperature durability are shown for exhaust gas which contains a reductive component containing hydrocarbon and oxygen excessive more than stoichiometric quantity necessary to completely oxidize the whole reductive component and nitrogen oxide.