The present invention relates to a wireless communication system. Particularly, a method by which a terminal scans a base station in a plurality of communication systems, according to one embodiment of the present invention, can comprises the steps of: receiving, by the terminal connected to a first communication system, information on at least one second base station of a second communication system from a first base station of the first communication system; receiving, from the first base station, a scanning request message requesting to scan at least one second base station if a scanning start condition is satisfied, receiving; scanning at least one second base station on the basis of the scanning request message; and transmitting, to the first base station, a failure reporting message including information on the cause of a scanning failure if the result from the scanning step is failure.