The present invention relates to a method and a device by which a user equipment monitors a downlink control channel in a wireless communication system. More specifically, the method comprises a step of monitoring the downlink control channel on a flexible downlink subframe, wherein the flexible downlink subframe is obtained by reconfiguring, for downlink communication, an uplink subframe configured according to a reference UL-DL configuration, the reference UL-DL configuration is configured by the combination of a first UL-DL configuration set for a first cell and a second UL-DL configuration set for a second cell, and the first UL-DL configuration and the second UL-DL configuration are configured so as to change the usage of wireless resources.