An internal-combustion engine control apparatus is obtained which can accurately perform the control toward an output target value by calculating an exhaust gas temperature more accurately, and eliminating discrepancies of a turbine flow-rate and a waste-gate-valve opening-degree. In the apparatus, a thermal efficiency calculation unit calculates thermal efficiency based on a combination in any of ignition timing, charging efficiency, an air-fuel ratio and an exhaust gas recirculation (EGR) ratio being change factors in thermal efficiency of the internal-combustion engine; an exhaust-gas loss calculation unit calculates exhaust gas loss based on thermal efficiency calculated by the thermal efficiency calculation unit, and on a combination in any of the change factors of the exhaust gas loss; and an exhaust port temperature calculation unit calculates an exhaust gas temperature at an exhaust port portion based on exhaust gas loss calculated by the exhaust-gas loss calculation unit.