An engine output control apparatus of a power train employing an engine and an automatic transmission, capable of executing engine output control for excessive torque input prevention engine torque limiting action that prevents a torque input exceeding an upper limit of transmittable torque transmitted through the power train and for shift response control by which a shift speed increase of the automatic transmission is achieved during shifting, comprising: at least two different kinds of engine output control systems comprising at least a throttle opening control system having a superior steady-state stability, and an ignition timing control system having a superior transient response; characterized in a controller comprising: (a) a usable engine output control system decision circuit (S1; S11-S16) provided for making a check for each individual engine output control system enabled/disabled state to specify one or more usable engine output control systems by determining, based on an operating condition of the power train, whether each individual engine output control system is enabled or disabled for the engine output control to be executed for excessive torque input prevention engine torque limiting action and for shift response control; and (b) an engine output control system selection circuit (S2, S5; S17-S21) provided for commanding the throttle opening control system having the superior steady-state stability to execute both the engine output control for shift response control and the engine output control for excessive torque input prevention engine torque limiting action, when it is determined that the ignition timing control system is disabled and the throttle opening control system is enabled, and for commanding the ignition timing control system having the superior transient response to execute the engine output control for shift response control, and commanding the throttle opening control system having the superior steady-state stability to execute the engine output control for excessive torque input prevention engine torque limiting action, when it is determined that the ignition timing control system and the throttle opening control system are both enabled. at least two different kinds of engine output control systems comprising at least a throttle opening control system having a superior steady-state stability, and an ignition timing control system having a superior transient response; characterized in a controller comprising: (a) a usable engine output control system decision circuit (S1; S11-S16) provided for making a check for each individual engine output control system enabled/disabled state to specify one or more usable engine output control systems by determining, based on an operating condition of the power train, whether each individual engine output control system is enabled or disabled for the engine output control to be executed for excessive torque input prevention engine torque limiting action and for shift response control; and (b) an engine output control system selection circuit (S2, S5; S17-S21) provided for commanding the throttle opening control system having the superior steady-state stability to execute both the engine output control for shift response control and the engine output control for excessive torque input prevention engine torque limiting action, when it is determined that the ignition timing control system is disabled and the throttle opening control system is enabled, and for commanding the ignition timing control system having the superior transient response to execute the engine output control for shift response control, and commanding the throttle opening control system having the superior steady-state stability to execute the engine output control for excessive torque input prevention engine torque limiting action, when it is determined that the ignition timing control system and the throttle opening control system are both enabled. (a) a usable engine output control system decision circuit (S1; S11-S16) provided for making a check for each individual engine output control system enabled/disabled state to specify one or more usable engine output control systems by determining, based on an operating condition of the power train, whether each individual engine output control system is enabled or disabled for the engine output control to be executed for excessive torque input prevention engine torque limiting action and for shift response control; and (b) an engine output control system selection circuit (S2, S5; S17-S21) provided for commanding the throttle opening control system having the superior steady-state stability to execute both the engine output control for shift response control and the engine output control for excessive torque input prevention engine torque limiting action, when it is determined that the ignition timing control system is disabled and the throttle opening control system is enabled, and for commanding the ignition timing control system having the superior transient response to execute the engine output control for shift response control, and commanding the throttle opening control system having the superior steady-state stability to execute the engine output control for excessive torque input prevention engine torque limiting action, when it is determined that the ignition timing control system and the throttle opening control system are both enabled.