Display apparatus and support method using the portable terminal and the external device

A display device using a portable terminal and an external device and a method are provided to display data of the terminal on a screen of the external device through link between the terminal and the external device, and to display data on a screen of the displayed data through interworking the portable terminal with the external device, thereby increasing usage efficiency of the terminal. User data in accordance with a user's request is outputted(401). While the user data is outputted, a screen display mode is executed according to the user's request(403). After the screen display mode is executed, screen display data in accordance with the user's request is simultaneously outputted by displaying the outputted user data(405-409). The user data includes at least one of text documents within a portable terminal, video data, image data, and externally received broadcasting data.