A preceding-vehicle following control system for a host vehicle is comprised of a road information device (2, 3) for obtaining road information of a road ahead of the host vehicle, a preceding-vehicle detector (1) for obtaining preceding-vehicle information of a preceding vehicle ahead of the host vehicle and a controller (10) connected to the road information device and the preceding vehicle recognizing device. The controller is arranged to determine a road width of the road from the road information, to vary a condition for determining a control characteristic of a control system of a following control for following the preceding vehicle, and to execute the following control on the basis of the condition for determining the control characteristic and the preceding-vehicle information.