An object of the present invention is to suppress a reduction in an NOX purification ratio when an addition is implemented to prevent a blockage from occurring in a reducing agent addition valve. A fuel addition valve, a catalyst having an oxidation capacity, and a selective reduction type NOX catalyst are provided in sequence in an exhaust passage of an internal combustion engine, and when a temperature of the selective reduction type NOX catalyst is within a predetermined temperature range while a predetermined condition for injecting fuel from the fuel addition valve is established, an amount of fuel injected from the fuel addition valve is reduced below an amount of fuel injected when the temperature of the selective reduction type NOX catalyst is outside the predetermined temperature range.