The present invention relates to a wireless communication system and, more particularly, to a method and a device for transmitting control information. The wireless communication system supports carrier aggregation (CA). One aspect of the present invention relates to a method for a base station to receive information from a terminal in a wireless communication system, and comprises the steps of: dividing the entire bandwidth used by one or more serving cells configured in the base station and the terminal, into predetermined frequency units; carrying out a carrier sensing operation for each of the plurality of bandwidths divided in the predetermined frequency units; and when the result of the carrier sensing operation for a first bandwidth from the plurality of divided bandwidths is maintained idle for a predetermined time or longer, transmitting first information to the terminal using the first bandwidth; and receiving from the terminal, second information on a second cell (SCell) related to the first information from the one or more serving cells.