An ECU controls an adjusting mechanism adjusting an output of an engine, such as a throttle valve, a swirl control valve, an ignition plug, an intake valve, and an ACIS (Acoustic Control Induction System) changing the length of an intake manifold, in accordance with a ratio between a maximum value KL(MAX) of load factor and the load factor required of the engine by the driver and by the system mounted on the vehicle at current engine speed NE.