Fuel supply amount controller of internal combustion engine and method for controlling the same

A controller controls an amount of fuel supplied to an internal combustion engine of a vehicle. The controller restricts the fuel supply amount, which is requested for the engine, in accordance with a fail-safe limit value set correspondingly to an operation state of the engine. The controller includes changing means. When a supplemental fuel injection amount, which is requested for causing the engine to generate output torque required for purposes other than driving the vehicle, is set, the changing means causes the limit value to be equal to or to approach the supplemental fuel injection amount if the limit value is less than the supplemental fuel injection amount. Therefore, the controller corresponds to a request for causing the engine to generate output torque required for purposes other than driving the vehicle.