In an auto-cruise system for a vehicle, when a distance detected by a distance detecting device becomes shorter than a reference distance based on a value detected by a vehicle speed detecting device, a speed reducing command signal is output from a distance regulating device. A travel speed control device is capable of being switched over among a cruise speed control mode for controlling the vehicle speed such that a vehicle speed is equalized to a vehicle speed set by a speed setting device upon non-outputting of a speed reducing command signal, a speed reducing control mode for reducing the vehicle speed upon outputting of the speed reducing command signal, and a speed increasing control mode for increasing the vehicle speed until it is restored to the set vehicle speed in response to the disappearing of the speed reducing command signal. In the speed increasing control mode of the travel speed control device, the acceleration until the restoration of the vehicle speed to the set vehicle speed is set such that it is lowered as the turning state detected by a turning state detecting device is enlarged. Thus, the restoration to the set vehicle speed after speed-reduction can be smoothed to ensure that a driver does not feel a discomfort or a sense of incompatibility.