A control device is provided that generates a target air-fuel ratio by lessening a change speed of a required air-fuel ratio of an internal combustion engine. However, when a deterioration degree of a catalyst which is disposed in an exhaust passage of the internal combustion engine is a predetermined reference or more, lessening of the change speed of the required air-fuel ratio is stopped, or a lessening degree of the change speed of the required air-fuel ratio is decreased. The control device calculates a target air quantity for realizing the required torque under the target air-fuel ratio. For calculation of the target air quantity, data in which relationship of torque generated by the internal combustion engine and an air quantity taken into a cylinder is fixed by being related to an air-fuel ratio can be used.