An initial movement state of a vehicle is specified in which a starting-off or acceleration is enabled by stepping on an accelerator pedal. In the specified initial movement state, a starting-off direction of the vehicle and an obstacle existing in the starting-off direction are specified. In the initial movement state, an incorrect starting-off sign action is detected which a driver of the vehicle indicates in a duration prior to the time when the vehicle practically starts off. When the incorrect starting-off sign action is detected, an incorrect starting-off prevention output is performed.