An exhaust gas purification system which feeds hydrocarbon by a post-injection under preset conditions to an upstream side of an exhaust gas purification device positioned on the exhaust path of an internal combustion engine, restoring the purifying capacity of the device or purifying the exhaust gas of the device. Under hydrocarbon feed conditions, if a combination of the exhaust gas temperature and exhaust gas flowrate or intake flowrate during control is deemed to be in a misfire region in which hydrocarbon which is fed to the exhaust path no longer combusts in the exhaust gas purification unit, the feed of hydrocarbon is stopped. As a result, it is possible to prevent deposit of hydrocarbon on catalysts or other exhaust gas purification units of the device, making it possible to constantly maintain the temperature of the unit in a controllable state.