1. An electronic device, comprising: a sensor configured to detect a location of at least one viewer; a display configured to display a three-dimensional (3D) image, and the display to provide at least one 3D-visible area and at least one 3D-invisible area, the 3D-visible area being an area where a 3D image is to be recognized by a viewer and the 3D-invisible area being an area where a 3D image is not to be recognized by a viewer; a controller configured to change a display state of a displayed image when the viewer is detected to be at the 3D-invisible area, and wherein the controller is configured to provide a two-dimensional (2D) image corresponding to a location of a viewer provided at the 3D-invisible area such that the display state of the image is changed to a 2D state.