A control apparatus of an internal combustion engine in which a plurality of cylinders is divided into a first cylinder group (1a) and a second cylinder group (1b), the internal combustion engine being able to be selectively switched between operating in a partial cylinder operation mode in which only one of the first cylinder group (1a) and the second cylinder group (1b) is operated, and operating in a full cylinder operation mode in which both the first cylinder group (1a) and the second cylinder group (1b) are operated. This control apparatus includes a supercharger (8), as well as a controller (30) that selectively starts and stops operation of the supercharger (8) depending on a load on the internal combustion engine when the internal combustion engine is to be operated in the partial cylinder operation mode.