Provided are a method for monitoring downlink control information by user equipment in a wireless communication system and user equipment using the method. The method comprises: receiving “control channel candidate number information” indicating the number of control channel candidates for each aggregation level (AL) of a search space (SS) per cell; and in order to detect DCI, monitoring some initial control channel candidates among existing control channel candidates (legacy candidates), wherein the number of the initial control channel candidates is determined based on the control channel candidate number information.