A method for supplying an N-screen service by a main N-screen device in a broadcast system, the method comprising: receiving an application information table, AIT, including a screen type indicating a type of N-screen device in which a broadcast service application is to be run from a broadcast service provider, wherein the type of N-screen device is one of "Main" indicating that the broadcast service application is run on the main N-screen device, "Sub_Alternative" indicating that the broadcast service application is preferentially run on a sub N-screen device and the broadcast service application is run on the main N-screen service if there is no sub N-screen device, and "Sub" indicating that the broadcast service application is not run if there is no sub N-screen device; determining the screen_type in the AIT; if the determined screen_type is the "Main", running the broadcast service application; if the determined screen_type is not the "Main", determining whether the main N-screen device is connected to the sub N-screen device; if the main N-screen device is not connected to the sub N-screen device, determining whether the determined screen_type is the "Sub"; if the determined screen_type is the "Sub", discarding the AIT; if the determined screen_type is not the "Sub", determining whether the determined screen_type is the "Sub_Alternative"; if the determined screen_type is the "Sub_Alternative", running the broadcast service application in the main N-screen device; if the determined screen_type is not the "Sub_Alternative", finishing the N-screen service; if the main N-screen device is connected to the sub N-screen device, determining whether the sub N-screen device is a hybrid terminal; if the sub N-screen device is the hybrid terminal, transmitting the AIT to the sub N-screen device; if the sub N-screen device is not the hybrid terminal, receiving broadcast service application data corresponding to the broadcast service application from the broadcast service provider; and transmitting the broadcast service application data to the sub N-screen device. receiving an application information table, AIT, including a screen type indicating a type of N-screen device in which a broadcast service application is to be run from a broadcast service provider, wherein the type of N-screen device is one of "Main" indicating that the broadcast service application is run on the main N-screen device, "Sub_Alternative" indicating that the broadcast service application is preferentially run on a sub N-screen device and the broadcast service application is run on the main N-screen service if there is no sub N-screen device, and "Sub" indicating that the broadcast service application is not run if there is no sub N-screen device; determining the screen_type in the AIT; if the determined screen_type is the "Main", running the broadcast service application; if the determined screen_type is not the "Main", determining whether the main N-screen device is connected to the sub N-screen device; if the main N-screen device is not connected to the sub N-screen device, determining whether the determined screen_type is the "Sub"; if the determined screen_type is the "Sub", discarding the AIT; if the determined screen_type is not the "Sub", determining whether the determined screen_type is the "Sub_Alternative"; if the determined screen_type is the "Sub_Alternative", running the broadcast service application in the main N-screen device; if the determined screen_type is not the "Sub_Alternative", finishing the N-screen service; if the main N-screen device is connected to the sub N-screen device, determining whether the sub N-screen device is a hybrid terminal; if the sub N-screen device is the hybrid terminal, transmitting the AIT to the sub N-screen device; if the sub N-screen device is not the hybrid terminal, receiving broadcast service application data corresponding to the broadcast service application from the broadcast service provider; and transmitting the broadcast service application data to the sub N-screen device.