The present invention relates to a method and device for monitoring the control channel in a multiple carrier system. A terminal determines an extended search space comprising a plurality of sub-search spaces, and each of the plurality of sub-search spaces corresponds to at least one of a plurality of scheduled component carriers. The terminal monitors a downlink control channel for the scheduled component carrier corresponding to each of the plurality of sub-search spaces. At least one of the plurality of sub-search spaces is a shared sub-search space corresponding to at least two of the plurality of scheduled component carriers.