The present invention relates to a wireless communication system, and specifically to a method and a device therefor, the method comprising: a step for receiving group common DCI on a first cell, wherein the group common DCI includes availability information about one or more RB sets configured for the first cell; a step for, on the basis of all of the RB set(s) being indicated as unavailable, performing first PDCCH monitoring, but skipping channel measurement on the RB set(s) during a certain duration; and a step for, on the basis of at least one of the RB set(s) being indicated as available, performing second PDCCH monitoring and the channel measurement on the at least one available RB set.