An engine control device including an ion signal detection means for detecting ions generated during combustion and an abnormal combustion determination means for determining an occurrence of knocking or misfiring by means of an ion signal detected by the detection means, the engine control device characterized in comprising: an in-cylinder temperature estimation means for estimating an in-cylinder temperature in a normal combustion cycle under current operating conditions of an engine, wherein a knocking determination threshold value or a misfiring determination threshold value of the ion signal is set on the basis of estimated in-cylinder temperature information, wherein the in-cylinder temperature estimation means estimates the in-cylinder temperature by use of at least one of internal pressure of an intake pipe of the engine, opening-closing timings of an intake valve and an exhaust valve that control air intake and air exhaust of the engine, an air-fuel ratio that is a mass ratio of air to fuel fed to an interior of a combustion chamber of the engine, and an ignition signal for controlling ignition timing of the engine; and the engine control device further comprising: a steady state operation determination means for determining whether or not a current operation state of the engine is a steady operation state, wherein, when the steady state operation determination means determines that the current operation state of the engine is not a steady operation state, the knocking determination threshold value or the misfiring determination threshold value of the ion signal is set on the basis of the in-cylinder temperature information; wherein, when the steady state operation determination means determines that the current state is the steady operation state, the knocking determination threshold value or the misfiring determination threshold value is set on the basis of an average of ion signals for a predetermined number of cycles prior to a current cycle detected by the ion signal detection means. an in-cylinder temperature estimation means for estimating an in-cylinder temperature in a normal combustion cycle under current operating conditions of an engine, wherein a knocking determination threshold value or a misfiring determination threshold value of the ion signal is set on the basis of estimated in-cylinder temperature information, wherein the in-cylinder temperature estimation means estimates the in-cylinder temperature by use of at least one of internal pressure of an intake pipe of the engine, opening-closing timings of an intake valve and an exhaust valve that control air intake and air exhaust of the engine, an air-fuel ratio that is a mass ratio of air to fuel fed to an interior of a combustion chamber of the engine, and an ignition signal for controlling ignition timing of the engine; and the engine control device further comprising: a steady state operation determination means for determining whether or not a current operation state of the engine is a steady operation state, wherein, when the steady state operation determination means determines that the current operation state of the engine is not a steady operation state, the knocking determination threshold value or the misfiring determination threshold value of the ion signal is set on the basis of the in-cylinder temperature information; wherein, when the steady state operation determination means determines that the current state is the steady operation state, the knocking determination threshold value or the misfiring determination threshold value is set on the basis of an average of ion signals for a predetermined number of cycles prior to a current cycle detected by the ion signal detection means.