INTERNAL COMBUSTION ENGINE CONTROL DEVICE AND INTERNAL COMBUSTION ENGINE CONTROL METHOD

Provided is an internal combustion engine control device that is capable of accurately estimating a stable combustion state at low cost. An internal combustion engine control device according to one aspect of the present invention includes: a rotational speed calculation unit that calculates a time-series value of a crank rotational speed of an internal combustion engine; a rotational, speed phase calculation unit that calculates a phase of the crank rotational speed from the time-series value of the crank rotational speed calculated by the rotational speed calculation unit; and a cycle variation calculation unit that calculates the magnitude of variation between cycles of the phase of the crank rotational speed calculated by the rotational speed phase calculation unit.