To reduce amount of emission of NOx and particulates contained in the exhaust gas, as well as to prevent HCs produced by emission of hydrocarbon liquid into the atmosphere from discharging.

NOx occlusion reduction catalyst 24, carrying NOx absorbent and active metal, is set in an exhaust pipe 16 of an engine 11, a liquid injection nozzle 29, capable of ejecting the hydrocarbon liquid 32 toward NOx occlusion reduction catalyst is set in the exhaust pipe, the upper stream of the exhaust gas from the NOx occlusion reduction catalyst. A hydrocarbon liquid feed means 36, for feeding liquid via a liquid-regulating valve 34 is set in the liquid ejecting nozzle, and a particulate filter 26 carrying an active metal, functioning as oxidation catalyst is set in the exhaust pipe, downstream of the exhaust gas from the NOx occlusion reduction catalyst. NOx occlusion reduction catalyst is made of a platinum-barium-alumina catalyst, and the particulate filter is coated with either the platinum-zeolite catalyst or platinum-ceria-zeolite catalyst.