The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for performing a random access procedure in wireless communication system, the method comprising: starting a timer when a Msg3 for a RA procedure is transmitted to a base station; monitoring a Physical Downlink Control Channel (PDCCH) while the timer is running; and stopping the timer if the PDCCH including uplink resource for the retransmission of the Msg3 is received