The present invention relates to a wireless communication system, particularly, a method in which a terminal transmits control information in a CA-based wireless communication system and an apparatus for the method, the method comprising: configuring a first cell and a second cell having different subframe configurations, wherein the second cell has any one of UL-DL configuration #0 to #6; receiving a DC) format including a DAI field, for the second cell; and transmitting HARQ-ACK information relating to the downlink DCI format. For HARQ-ACK timing, in cases where a reference UL-DL configuration applied to the second cell is any one of UL-DL configurations #1 to #6, the DAI field is used in a process of transmitting the HARQ-ACK information. For HARQ-ACK timing, in cases where a reference UL-DL configuration applied to the second cell is #0, the DAI field is not used in a process of transmitting the HARQ-ACK information.