There is provided an exhaust gas purification apparatus for an engine capable of effectively removing NOx in exhaust gas even when the temperature of exhaust gas is relatively low. The exhaust gas purification apparatus includes a selective reduction catalyst provided in an exhaust pipe, a liquid injection nozzle provided on the upstream side of the selective reduction catalyst, a liquid injecting means capable of injecting a urea-based liquid via the liquid injection nozzle, a controller, and a mixer. The apparatus further includes an ammonia purification catalyst provided on the downstream side of the selective reduction catalyst, a diesel particulate filter provided on the upstream side of the nozzle, an oxidation catalyst provided on the upstream side of the diesel particulate filter, and a temperature sensor for detecting the temperature of the selective reduction catalyst. A fuel injection device is configured so as to be capable of injecting fuel into a cylinder after the top dead center of piston, and when the temperature sensor detects that the selective reduction catalyst has a temperature not higher than a predetermined temperature, the controller controls the fuel injection device so that fuel is injected into the cylinder after the top dead center of piston.