A method by which a terminal transmits uplink control information (UCI) in an unlicensed band and a device using the method are provided. The method generates data and first UCI including information necessary to decode the data, and transmits, to a base station, the data and the first UCI through a physical uplink shared channel (PUSCH) in an unlicensed band, wherein the first UCI further includes information necessary to decode the second UCI when second UCI is transmitted to the base station together with the data and the first UCI through the PUSCH.