In an internal combustion engine, an NOx selective reducing catalyst is arranged inside an engine exhaust passage, an oxidation catalyst is arranged upstream of the NOx selective reducing catalyst, and an NOx adsorption catalyst is arranged upstream of the oxidation catalyst. The NOx adsorption catalyst has a property of releasing NOx when the temperature rises and a property of trapping the SOx contained in the exhaust gas. The inflow of SOx into the oxidation catalyst is suppressed by the NOx adsorption catalyst to prevent the NO released from the NOx adsorption catalyst being oxidized to NO2 at the oxidation catalyst from being obstructed by SOx.