An object of the present invention is to enable a requested efficiency by cylinder group that is requested from a viewpoint of exhaust gas performance to be realized precisely when an internal combustion engine having a single throttle shared by a plurality of cylinder groups, and having an exhaust gas purifying catalyst for each of the cylinder groups is operated at a different air-fuel ratio at each of the cylinder groups. To this end, a control device for the internal combustion engine provided by the present invention calculates an efficiency ratio of a representative efficiency determined based on the requested efficiency by cylinder group and a requested efficiency by cylinder group, and calculates a requested torque by cylinder group by dividing a requested torque by the efficiency ratio for each of the cylinder groups. The control device controls an opening of the throttle in accordance with the requested torque, the representative efficiency based on the requested efficiency by cylinder group, and a target air amount calculated from a representative air-fuel ratio based on a target air-fuel ratio by cylinder group, and controls ignition timing for each of the cylinder groups, in accordance with a target efficiency by cylinder group that is calculated as a ratio of the requested torque by cylinder group and an estimated potential torque.