The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for performing UL packet delay measurement in a wireless communication system, the method comprising: checking whether a value of queuing delay of a PDCP SDU is above a threshold, and generating and transmitting a PDCP PDU including the PDCP SDU and a time stamp for the PDCP SDU, if the value of the queuing delay is above the threshold, wherein a value of the time stamp for the PDCP SDU is set to a time when the PDCP SDU is received from the upper layer.