The present invention relates to a wireless communication system. Specifically, the present invention relates to a method for transmitting, by a terminal, control information in an FDD cell, and an apparatus therefor, the method comprising the steps of: receiving sub-frame reconfiguration information for a UL CC; receiving, on the FDD cell, a PDCCH including DCI; receiving, on the FDD cell, a PDSCH indicated by the PDCCH; and transmitting, on the UL CC, HARQ-ACK information on the PDSCH, wherein if the PDSCH is received on a DL CC, the DCI does not include a DAI field, and if the PDSCH is received in the UL CC, the DCI includes a DAI field.