Abstract: A throttle control apparatus that maintains a vehicle's ability to run during a throttle system failure includes a throttle-controlling ECU that calculates a throttle opening instruction value from an accelerator stroke signal outputted from an accelerator pedal sensor, and supplies a motor with a current value based on the instruction value, to control the opening of a throttle valve. If the deviation between the instruction value and the output value from a throttle sensor is greater than a reference value, the ECU determines that there is a system failure. If it is determined that a system failure exists, an internal combustion engine controlling ECU varies the number of cylinders of the engine in operation to vary the engine output, depending on whether the amount of depression of the accelerator pedal by the driver is greater than a predetermined value.