Provided is an exhaust gas purification system which is capable of accurately controlling idling mode automatic regeneration when a vehicle is stopped during running mode automatic regeneration and also preventing the temperature of exhaust gas from overshooting even when the idling mode automatic regeneration is shifted to running mode automatic regeneration. In the exhaust gas purification system, a DPD 25 for trapping PM in exhaust gas is connected to an exhaust pipe 20 of a diesel engine 10 to automatically regenerate the DPD by raising a temperature of the exhaust gas from a diesel engine 10 by carrying out post injection when an amount of PM in the DPD 25 exceeds a predetermined amount. Further, the system includes detecting the temperature of the exhaust gas during DPD regeneration when the DPD is automatically regenerated, calculating a deviation between the detected temperature of the exhaust gas and a target temperature for the DPD regeneration, and controlling a quantity of the post injection by resetting an integral control term used in a PID control to zero when running mode automatic regeneration is shifted to idling mode automatic regeneration after a vehicle is stopped, when PID-controlling the quantity of the post injection based on the deviation.