Abstract: An auto cruise control method and device for a vehicle such as a motorcycle allows the vehicle to operate at a constant set speed while avoiding acceleration or deceleration shock after the auto cruise device is temporarily or permanently operated to change the vehicle speed. Therefore, a smoother ride is provided. Also, a final acceleration change rate can be corrected by considerating factors such as slope, wind, load weight, variation in engine output and non-linearity of engine torque characteristics. Moreover, when the speed is to be changed or when operation of the auto cruise device is to be resumed, the speed of the vehicle can be smoothly shifted.