An internal combustion engine (1) for a vehicle is equipped with a variable compression ratio mechanism (2) capable of changing the mechanical compression ratio. An idle stop, which is for automatically stopping the internal combustion engine (1) when the vehicle stops, and a sailing stop, which is for stopping the internal combustion engine (1) in conjunction with the release of a forward clutch (8) during inertial travel, are carried out. A target compression ratio during normal travel is set on the basis of the load and rotation speed of the internal combustion engine (1). During an idle stop the target compression ratio is set to an idle stop restart compression ratio (εis). During a sailing stop the target compression ratio is set to a sailing stop restart compression ratio (εss). The sailing stop restart compression ratio (εss) is lower than the idle stop restart compression ratio (εis).