A method whereby a user equipment (UE) transmits hybrid automatic repeat request (HARQ) acknowledgement (ACK)/negative ACK (NACK) information corresponding to downlink data received from a corresponding base station (ENB) in a long term evolution-advanced (LTE-A) system supporting carrier aggregation (CA) is provided. When physical uplink shared channel (PUSCH) transmission is not scheduled at the time of transmission of HARQ ACK/NACK information, the UE transmits HARQ ACK/NACK information via physical uplink control channel (PUCCH). When PUSCH transmission is scheduled, the UE transmits HARQ ACK/NACK information multiplexed with PUSCH to the ENB. The amount of HARQ ACK/NACK information increases in proportion to the number of aggregated carriers. The present disclosure specifies scheduling operation of the ENB and HARQ ACK/NACK mapping of the UE that maintain reception performance of HARQ ACK/NACK and PUSCH when HARQ ACK/NACK information is multiplexed with PUSCH.