A three-dimensional display device according to the present invention includes a panel that time-shares images and displays left and right eye images, a panel control unit for controlling the panel by applying a display control signal that includes vertical and horizontal signals to the panel, a barrier facing the panel and separating the images of the panel into user left and right eye images, and a barrier control unit for controlling the barrier. The panel can be converted between a first mode of a portrait-type view and a second mode of a landscape-type view, and the barrier may be operated corresponding to the mode conversion of the panel.