An ECU controls waste heat quantity of an engine according to a required heat quantity in response to a heat-utilize requirement. The ECU controls a valve opening period of an intake valve based on an engine driving condition and an ignition timing based on a most efficient timing at which fuel economy is highest. The ECU determines whether there is an ignition advance margin relative to the most efficient timing. When there is no margin, an actual compression ration of the engine is decreased by advancing or retarding a valve close timing of the intake valve and the ignition timing is advanced relative to the most efficient timing in order to increase the waste heat quantity.