The present disclosure discloses a method and an apparatus for transmitting hybrid automatic repeat request acknowledgement (HARQ-ACK) information by a user equipment (UE) in a wireless communication system supporting carrier aggregation (CA), the method comprises receiving a downlink signal from a base station, determining the number of bits of HARQ-ACK information for cells configured for the UE on the basis of at least one of an uplink downlink assignment index (UL DAI), the number of downlink subframes, the number of the cells configured for the UE, which are acquired from the downlink signal, and a transmission mode, and transmitting an uplink subframe including the HARQ-ACK information for the cells.