A brake override system (BOS) (1) prioritizes braking when both an accelerator and a brake are operated simultaneously by reducing the required accelerator operation amount value that is used to control drive force so that it is lower than the actual accelerator operation amount. The BOS (1) thus achieves a balance between hill-start performance after operation by the BOS (1) is cancelled and stopping performance during operation of the BOS (1) by increasing the required accelerator operation amount value at the time at which the return of the required accelerator operation amount value to the actual accelerator operation amount is initiated when the simultaneous operation of the accelerator and the brake ends.