A method for application extension and an image display apparatus using same. The method can include displaying a menu, receiving a selection signal selecting one or more external devices to display an application from the menu, detecting the external devices, receiving first application data of the application from a first external device and second application data of the application from a second external device, displaying an application execution screen based on the received first and second application data, receiving third application data of the application from at least one of the first external device or the second external devices, and displaying an execution screen of the application based on the received first, second and third application data. Also, the first, second and third application data can be processed by the first and second external devices, and the application does not have to be installed in the image display apparatus.