The invention provides a technology that enables to control response delay of the supercharger in a variable compression ratio internal combustion engine under acceleration. When the variable compression ratio internal combustion engine is under acceleration, the compression ratio of the internal combustion engine is set to a compression ratio lower than a basic compression ratio that is so determined in accordance with the running condition of the internal combustion engine to realize a predetermined heat efficiency while suppressing knocking, thereby raising the exhaust gas pressure and shortening the response time of the supercharger.