Apparatus and method of interface in multitasking system

A user interface method and apparatus are provided to facilitate movement between multiple applications which are simultaneously performed in a multitasking system so that user convenience can be improved, multiple application pictures can be simultaneously checked, and a currently selected application picture can be displayed without covering other application pictures. A user interface method comprises the following steps. A representative picture display request is received(500). Applications to be displayed on a requested representative picture are retrieved(502). A size and position of a display area to be allocated to the retrieved applications are determined according to characteristic values of the applications(504). The applications are displayed on areas of display means of a set-top box according to the determined size and position of the display area(506).