Internal combustion engine according to the invention comprises an exhaust treatment apparatus provided in an exhaust passage, a burner apparatus provided upstream of the exhaust treatment apparatus for increasing exhaust temperature, and a variable mechanism for varying valve timing of an exhaust valve. The variable mechanism is controlled in such a manner that, when a flow amount of exhaust gas passing through the burner apparatus is equal to or more than a predetermined value, the exhaust valve opens in the middle of piston descending during an expansion stroke. When the exhaust valve is opened at this timing, high-temperature exhaust or combustion gas existing in combustion chamber at this time is sent to the burner apparatus, making it possible to increase atmosphere gas temperature of the burner apparatus. Therefore, even when flow amount of exhaust gas is increased to the predetermined value or more, sufficient ignition performance can be ensured.