Disclosed herein a user interface device includes a display; a rail extending in a first direction parallel to the display; a hinge configured to slide along the rail in the first direction; a knob coupled to the hinge to slide in the first direction on a display surface and configured to detect a rotation input; and a magnet holder disposed to face the hinge in a second direction of the hinge and extending in the first direction; wherein the first magnet is provided on the hinge, the magnet holder is provided with a second magnet and a third magnet, the second and third magnets have different magnetic poles from that of the first magnet on facing surface thereagainst, and the first magnet reacts by an magnetic force of the second and third magnets so that the knob is held to a first position or a second position, respectively.