Variable compression ratio internal combustion engine

In a variable compression ratio internal combustion engine whose compression ratio is varied by changing the volume of a combustion chamber, the present invention is intended to enable the engine to operate at a high compression ratio under a much higher load while suppressing an excessive rise in the temperature of the combustion chamber. A cooling system is provided for cooling the variable compression ratio internal combustion engine, and when the load of the variable compression ratio internal combustion engine is equal to a specified value or above at a high compression ratio ( S101, S102 ), the cooling capacity of the cooling system is increased more than when the load of the variable compression ratio internal combustion engine is lower than the specified value ( S103 ), whereby a temperature rise in the combustion chamber can be suppressed.