The purpose of the present invention is to provide a method for increasing data transmission efficiency when performing packet duplication. A method for a terminal in a wireless communication system according to the present invention comprises the steps of: performing protocol data convergence protocol (PDCP) duplication in which an identical PDCP protocol data unit (PDU) is transmitted to a base station through each of a first logical channel and a second logical channel; when a request for retransmission of the PDCP PDU which has been transmitted through the second logical channel is received from the base station, retransmitting the PDCP PDU to the base station; and when the PDCP PDU has been retransmitted a predetermined number of times or more, receiving, from the base station, information indicating deactivation of the PDCP duplication.