A device performs speed control, determines the start and the end of an intervention operation, interrupts the speed control when an intervention operation is started, selects a correction candidate from a target speed and a target inter-vehicle distance based on the presence of a preceding vehicle and on the speed difference between the vehicle and the preceding vehicle, determines whether there is a change in the vehicle speed or in the inter-vehicle distance in a determination period, determines whether there is a difference between the target speed and the vehicle speed when the intervention is ended or between the target inter-vehicle distance and the inter-vehicle distance when the intervention is ended, and corrects the target speed or the target inter-vehicle distance under a predetermined condition. After the intervention operation is ended, the device restarts the speed control using the corrected target speed or the corrected target inter-vehicle distance.