When a preceding vehicle (Vb) starts during deceleration of a vehicle (Va) which is trying to stop following the stopped preceding vehicle (Vb), if the vehicle (Va) accelerates following the preceding vehicle (Vb), the driver possibly mistakes that the vehicle is equipped with an automatic start function. A virtual preceding vehicle (Vb′) is set at the stop position of the preceding vehicle (Vb), so that the vehicle (Va) is temporarily stopped following the stopping virtual preceding vehicle (Vb′) even if the actual preceding vehicle (Vb) is started. As a result, the vehicle (Va) is not started until the driver indicates the intention to start by operating a start switch, and the driver can be prevented from mistaking that the vehicle is equipped with an automatic start function.