The general purpose of the present disclosure is to retransmit data between base stations in a wireless communication system, and an operating method of a base station comprises the steps of: receiving, from another base station, information on unreceived packets; and retransmitting at least one unreceived packet among the unreceived packets to another base station based on the received information, wherein the at least one unreceived packet is determined based on a difference value between an identification number of the unreceived packets and an identification number of a last packet transmitted to the other base station.