The present invention features a user interface device for controlling a car multimedia system that preferably includes a remote touchpad unit, a display unit displaying various kinds of modes of a multimedia system in accordance with a three-dimensional signal received from the remote touchpad unit, and a control unit controlling to operate the multimedia system in accordance with the three-dimensional signal provided from the remote touchpad unit. According to the user interface device, it is possible to manipulate a multimedia system by a three-dimensional interaction using a remote touchpad unit to improve the utility. Accordingly, the danger of accident and the driver's loading can be suitably reduced.