To suppress deterioration of emission and drop of performance in an operation condition where combustion temperature gets high.

This internal combustion engine 1 is a reciprocating internal combustion engine provided with a water injection valve 3. Water I is supplied to a combustion chamber 1b by injecting water from the water injection valve 3. Timing of water injection from the water injection valve 3 is in a period of overlap of open timing of an intake valve 8i and close timing of an exhaust valve 8e. The combustion chamber 1b of the internal combustion engine 1 is cooled by injecting water from the water injection valve 3 during the overlap period and the injected water passes through an exhaust system of the internal combustion engine 1 to cool exhaust gas.