Provided is a backward motion control technology for a car. The car comprises a backward-motion control terminal, a control signal converter, and a backward-motion controller. The backward-motion control terminal outputs a first backward-motion control signal corresponding to a backward velocity and a backward direction of the last trailer according to a user's operation. The control signal converter converts the first backward-motion control signal to a second backward-motion control signal which corresponds to a backward velocity and a backward direction of the car. The backward-motion controller controls the car based on the second backward-motion control signal so that the last trailer moves backward by the backward velocity and the backward direction corresponding to the first backward-motion controlling signal.