Abstract: Provided is a method and apparatus for transmitting an HARQ ACK/NACK. The method includes: recognizing, from a PDCCH or an EPDCCH, a 2-bit uplink (UL) downlink assignment index (DAI) field configured in a UL downlink control information (DCI) format; receiving a PDSCH transmission through the second serving cell; generating an HARQ response signal based on the number of PDSCHs scheduled in the downlink subframes indicated by the UL DAI field and the number of total downlink subframes associated with one uplink subframe; and transmitting the HARQ response signal through a PUSCH in the one uplink subframe.