Described herein is a drive-by-wire vehicle engine output control system. The system permits good-response acceleration by a driver's simple and reasonable operation, i.e., by operating an accelerator pedal and also a prompt response even when a sudden load change occurs. Further, the system permits precise speed control by simple equipment even when the deviation of a vehicle speed from a target vehicle speed is large. Output changes of an engine can be controlled within a permissible output change range by (a) comparing a target autocruise engine output with an acceleration demanding ending output, choosing the larger engine output and then controlling the engine to give the larger engine output, (b) controlling the engine to achieve a target autocruise engine output obtained from a speed correction torque and a running load torque or (c) limiting an engine control quantity on the basis of a permissible output change value.