It is an object of the present invention to provide a control device for an internal combustion engine capable of appropriately controlling compression ratio and ignition timing before the target compression ratio that is set according to humidity is attained. A control device for an internal combustion engine controls the internal combustion engine including a cylinder, humidity detection means for detecting humidity of outside air supplied to the cylinder, a variable compression ratio mechanism for changing a compression ratio of the cylinder, and an ignition device igniting air-fuel mixture in the cylinder, and the control device includes: a compression ratio control unit controlling the variable compression ratio mechanism; and an ignition control unit controlling ignition timing of the ignition device, wherein corresponding characteristics between compression ratio and ignition timing are determined for each humidity according to a predetermined condition of an operation state of the internal combustion engine, the compression ratio control unit determines a target compression ratio of the variable compression ratio mechanism according to the detected humidity, and while the variable compression ratio mechanism changes a compression ratio to the target compression ratio, the ignition control unit controls the ignition device on the basis of corresponding characteristics determined according to the detected humidity.