Provided are an apparatus for processing adaptive video and a method of scaling video, which generate a graphical user interface (GUI) so that a GUI suitable for the screen size of a display device can be displayed according to the screen size of the display device. The apparatus can realize a GUI most suitable for the screen size of an external display device connected to the apparatus by enlarging or reducing the size of the GUI according to the screen size of the external display device, or by changing the arrangement of items arranged on the GUI.