In an aspect of the present invention, a method for a user equipment (UE) to perform reflective quality of service (QoS) in a wireless communication system may include the steps of receiving a downlink packet from a network, wherein the downlink packet is a packet to which the application of the reflective QoS is indicated; deriving a QoS rule based on the downlink packet; applying a QoS marking of the downlink packet to an uplink packet using the QoS rule and transmitting the uplink packet to the network; and restarting a timer associated with the QoS rule when the downlink packet is received before the timer expires.