A control device of an internal combustion engine includes: an air-fuel ratio modulator, performing modulation of an air-fuel ratio of an exhaust which flows in an exhaust purifier provided in an exhaust system of the internal combustion engine; a fluctuation detector, detecting a fluctuation of the internal combustion engine due to the modulation of the air-fuel ratio performed by the air-fuel ratio modulator; a feed-back controller, performing feed-back control of a driving control parameter of the internal combustion engine so as to suppress the fluctuation detected by the fluctuation detector; a determiner, determining whether or not a driving state of the internal combustion engine is in an operating area of the feed-back controller; and an operator, setting a fluctuation suppression target value, which is a target value for suppressing the fluctuation of the internal combustion engine, to operate the feed-back controller based on the fluctuation suppression target value, when the determiner determines that the driving state of the internal combustion engine is not in the operating area of the feed-back controller, while the air-fuel modulator performs the modulation of the air-fuel ratio.