The present invention relates to a method for offloading data in a wireless communication system for supporting a multiple radio access network and an apparatus for same. Specifically, the method includes the steps of: receiving a message of a connected cell report including an identifier of a wireless local area network (WLAN) access point (AP) to which a terminal is connected via a base station, from the terminal connected to the base station of a cellular network; transmitting scheduling information on a data transmission time to the base station, when data to be transmitted to the terminal is determined to be transmitted via the WLAN AP; and transmitting the data via the WLAN AP to the terminal according to the scheduling information.