An exhaust gas purifying system includes an exhaust gas purifying catalyst (14) having a nitrogen oxide absorbing material which is installed in an exhaust line (13) of an engine (1) and performs split fuel injection to inject fuel directly into each combustion chamber (5) partly during a suction stroke and partly during a compression stroke to provide and supply an increased amount of carbon monoxide to the nitrogen oxide absorbing material so as thereby to desorb sulfur oxides from the nitrogen oxide absorbing material.