The present invention relates to a wireless communication system. More specifically, the present invention relates to a method for transmitting control information and an apparatus therefor, the method comprising the steps of: detecting one or more PDSCHs on a plurality of cells, wherein the plurality of cells are divided into a first cell set having PCell and a first SCell, and a second cell set having one or more second SCells; and as feedback for the one or more PDSCHs, transmitting HARQ-ACK information over PUCCH, wherein when the one or more PDSCHs are detected only in the first cell set, the HARQ-ACK information contains only a HARQ-ACK response for the first cell set, and when the one or more PDSCHs are detected at least in the second cell set, the HARQ-ACK information contains HARQ-ACK responses for both the first and the second cell sets.