A method and device for transmitting acknowledgement/non-acknowledgement (ACK/NACK) by User Equipment (UE) for which a plurality of serving cells has been configured in a wireless communication system operating in Time Division Duplex (TDD). The method includes: configuring a plurality of serving cells; receiving a codeword through at least one of the plurality of configured serving cells; and transmitting ACK/NACK information indicative of reception acknowledgement for the codeword. Here, if the UE receives the codeword through only a first serving cell of the plurality of configured serving cells, the UE transmits the ACK/NACK information according to a first transmission scheme, and the first transmission scheme is a scheme for sending ACK/NACK when the UE receives only one configured serving cell.