The application provides a device for purifying exhaust gas to purify exhaust gas in an engine, that include an exhaust line through which exhaust gas discharged from the engine passes; a NOx storagecatalyst that is installed in the exhaust line to absorb a nitrogen oxide discharged from the exhaust gas and detach an absorbed nitrogen oxide when a temperature of a catalyst is higher than a predetermined value; and a three way catalyst (TWC) arranged in rear of the NOx storage catalyst for reducing the nitrogen oxide detached from the NOx storage catalyst, wherein the NOx storage catalyst includes an LTA zeolite catalyst.