An exhaust gas purification system (1) provided with an exhaust gas purification device (4), such as a NOx occlusion-reduction catalyst, in an exhaust passage (3) of an internal combustion engine (E), the exhaust gas purification device (4) purifying exhaust gas when the air-fuel ratio of exhaust gas in a lean state, and recovering purification ability when in a rich state. The system prevents highly dense, uncombusted fuel from acting as a binder that causes soot, together with the uncombusted fuel, to adhere to an EGR cooler (7) in an EGR passage (6) and thus clogging the EGR cooler (7). An uncombusted fuel adsorption device (20) for adsorbing uncombusted fuel is provided upstream to the EGR cooler (7) in the EGR passage (6), the uncombusted fuel adsorption device (20) adsorbing uncombusted fuel passing through the EGR passage (6) during a rich control.