An exhaust gas purification system including an exhaust gas purification device having an oxidation catalyst device including an oxidation catalyst and a diesel particulate filter (“DPF”) arranged in order from an upstream side, or a DPF carrying an oxidation catalyst in an exhaust passage of an internal combustion engine. At regeneration of the DPF, when a catalyst temperature index temperature (Tg2), indicating a temperature of the oxidation catalyst, becomes equal to a predetermined determining temperature (Tc1) or above, a temperature of the DPF is raised by supplying an unburned fuel to the upstream side of the oxidation catalyst to thereby oxidize the unburned fuel by the oxidation catalyst. The predetermined determining temperature (Tc1) is changed according to an engine speed Ne of the internal combustion engine. By so oxidizing the unburned fuel supplied into an exhaust gas by the oxidation catalyst, outflow of white smoke is prevented regardless of an operation state of the internal combustion engine.