An exhaust gas purification system which effectively prevents NH3 slip or misdiagnosis when an exhaust gas temperature is rapidly increased is provided. The exhaust gas purification system includes a SCR 41, an NOx sensor 22 which is provided on a downstream side of the SCR 41, and an NOx purifying controller 51 which controls an amount of urea water being ejected to the SCR 41 and performs an abnormality diagnosis based on a detection value of the NOx sensor 22, wherein the exhaust gas purification system includes an exhaust gas temperature sensor 21 which acquires temperature of the exhaust gas flowing into the SCR 41, a temperature increasing rate calculating unit 54 which calculates a temperature increasing rate at which the exhaust gas temperature acquired by the exhaust gas temperature sensor 21 reaches a second temperature from a predetermined first temperature, and a prohibiting unit 55 which prohibits abnormality diagnosis by the NOx purifying controller 51 in a case in which the temperature increasing rate calculated by the temperature increasing rate calculating unit 54 is higher than a predetermined determination threshold value.