Disclosed are an uplink transmission method in a wireless communication system and a device therefor. Particularly, a method for performing uplink transmission by a user equipment (UE) in an unlicensed band in a wireless communication system may comprise the steps of: sensing a channel in an entire uplink frequency band, and then sensing a channel in a predetermined resource area during a predetermined first time interval; and as a result of the channel sensing, when the channel is determined to be idle, performing uplink transmission to an eNB in an uplink resource area allocated by the eNB, wherein the uplink transmission may not be mapped in an area overlapping the predetermined resource area during a predetermined second time interval in the allocated uplink resource area.