In a control device for an internal combustion engine, which includes control unit that has a processor with a plurality of cores and that computes various tasks associated with operation of the internal combustion engine, the control unit includes a selecting unit, that selects at least one core used in the computation from among the plurality of cores, a computing unit that distributes the tasks to the at least one core selected by the selecting unit to perform computation, and an acquisition unit that acquires an engine, rotational speed of the internal combustion engine, and, when the engine rotational speed acquired by the acquisition unit is higher than or equal to a predetermined threshold, the selecting unit increases the number of the cores selected as compared with when the acquired engine rotational speed is lower than the predetermined threshold.