A first porous catalytic layer is provided in an exhaust passage, and a second porous catalytic layer is stacked on the exhaust-gas downstream-side surface of the first layer. The first layer includes an iron-zeolite catalyst to decrease 60% or more of NOx in the exhaust gas within an exhaust gas temperature range of 150-400° C. The second layer includes one or more of a single catalyst, a mixed catalyst, and a complex oxide catalyst selected from iron-alumina, iron-zirconia, iron-ceria, and iron-titania, to decrease 60% or more of NOx in the exhaust gas within an exhaust gas temperature range of 400-700° C. The first and second layers cooperatively exhibit catalytic activity to decrease 70% or more of NOx in the exhaust gas within an exhaust gas temperature range of 150 to 700° C.