Incorporated in an exhaust pipe are an HC-SCR NOx catalyst capable of reducing NOx at temperatures less than a set temperature T and a catalyzed particulate filter with an oxidation catalyst capable of reducing NOx at temperatures not less than the set temperature T. When an exhaust gas temperature is less than the set temperature T, fuel with a set flow rate Q is intermittently added from a fuel addition unit on an entry side of the HC-SCR NOx catalyst to the HC-SCR NOx catalyst; when the exhaust gas temperature is not less than the set temperature T, the fuel with flow rate Q′ not less than the set flow rate Q is temporarily rich-spike added from the fuel addition unit and is made arrival at a catalyzed particulate filter. With an active temperature range being expanded, exhaust emission control is performed in a wide temperature range.