The present invention relates to a method for adjusting a size of an information bit used in a control channel and an apparatus for performing the same. In addition, the present invention relates to a method for searching for a control channel including an information bit having an adjusted size. A method for receiving a physical downlink control channel (PDCCH) in a wireless access system for supporting multi-carriers as one embodiment of the present invention comprises the steps of: performing blind decoding in a search space allocated in a terminal to search for a PDCCH; and receiving the PDCCH including downlink control information (DCI) having a size adjusted in the search space. At this time, the size of the DCI can be adjusted by considering a bandwidth allocated in the terminal, a transmission mode of a component carrier (CC) allocated in the terminal, and the number of antennas of the terminal.