Provided is an internal combustion engine control unit that controls an engine by detecting combustion characteristics with a simple configuration robust to disturbance such as noise. Therefore, the internal combustion engine control unit (ECU 12) of the present embodiment includes a rotational speed calculation unit 122a that calculates a crank rotational speed of an internal combustion engine (engine 1); an extreme value timing calculation unit 122b that calculates an extreme value timing of the crank rotational speed calculated by the rotational speed calculation unit 122a; and a combustion state estimation unit (combustion phase calculation unit 122c) that estimates a combustion state based on the extreme value timing of the crank speed calculated by the extreme value timing calculation unit 122b.