To prevent a reduction in engine load detection accuracy due to variations in reluctor size within mass production tolerances, an engine control unit includes a pulse generator PC that detects a reluctor to output crank pulses. An angular velocity calculating unit calculates a first crank angular velocity on the basis of an interval between two crank pulses output in a predetermined section near compression top dead center TDC, and detects near overlap top dead center OLP the same reluctor used for calculating the first crank angular velocity to calculate a second crank angular velocity on the basis of an interval between generated two crank pulses. An engine load estimating unit calculates, as an engine load, a difference between the first crank angular velocity and the second crank angular velocity. The engine load is indicated mean effective pressure over a whole cycle including negative work done by the engine.