An exhaust gas purification system comprising: a selective catalytic reduction which is provided on an exhaust gas passage of an internal combustion engine and purifies NOx in exhaust gas by using ammonia generated from urea water as a reducing agent; an NOx sensor which is provided on the exhaust gas passage on downstream side further than the selective catalytic reduction; and control means configured for controlling an amount of urea water being ejected to the selective catalytic reduction and performing an abnormality diagnosis based on a detection value of the NOx sensor, characterized in that: the exhaust gas purification system comprises: exhaust gas temperature acquiring means configured for acquiring temperature of the exhaust gas flowing into the selective catalytic reduction; temperature increasing rate calculating means configured for calculating a temperature increasing rate at which an exhaust gas temperature acquired by the exhaust gas temperature acquiring means reaches a predetermined second temperature, which is higher than a predetermined first temperature, from the first temperature; and prohibiting means configured for prohibiting the abnormality diagnosis by the control means in a case in which the temperature increasing rate calculated by the temperature increasing rate calculating means is higher than a predetermined determination threshold value. a selective catalytic reduction which is provided on an exhaust gas passage of an internal combustion engine and purifies NOx in exhaust gas by using ammonia generated from urea water as a reducing agent; an NOx sensor which is provided on the exhaust gas passage on downstream side further than the selective catalytic reduction; and control means configured for controlling an amount of urea water being ejected to the selective catalytic reduction and performing an abnormality diagnosis based on a detection value of the NOx sensor, characterized in that: the exhaust gas purification system comprises: exhaust gas temperature acquiring means configured for acquiring temperature of the exhaust gas flowing into the selective catalytic reduction; temperature increasing rate calculating means configured for calculating a temperature increasing rate at which an exhaust gas temperature acquired by the exhaust gas temperature acquiring means reaches a predetermined second temperature, which is higher than a predetermined first temperature, from the first temperature; and prohibiting means configured for prohibiting the abnormality diagnosis by the control means in a case in which the temperature increasing rate calculated by the temperature increasing rate calculating means is higher than a predetermined determination threshold value. exhaust gas temperature acquiring means configured for acquiring temperature of the exhaust gas flowing into the selective catalytic reduction; temperature increasing rate calculating means configured for calculating a temperature increasing rate at which an exhaust gas temperature acquired by the exhaust gas temperature acquiring means reaches a predetermined second temperature, which is higher than a predetermined first temperature, from the first temperature; and prohibiting means configured for prohibiting the abnormality diagnosis by the control means in a case in which the temperature increasing rate calculated by the temperature increasing rate calculating means is higher than a predetermined determination threshold value.