The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for operating fast random access procedure in a wireless communication system, the method comprising: transmitting a RAP including a first RAP ID to an e-NodeB; starting monitoring a Physical Downlink Control Channel PDCCH addressed by RA-RNTI during RAR window; receiving, from the eNB, an indicator including at least one RAP ID, wherein one of the at least one RAP ID matches to the first RAP ID; and stopping monitoring the PDCCH addressed by RA-RNTI upon reception of the indicator.