The present invention relates to a wireless communication system. More particularly, the present invention relates to a method and a device therefor, the method comprising: setting a first cell having a first TDD UL-DL configuration and a second cell having a second TDD UL-DL configuration; receiving data through a DL subframe of the first cell; and transmitting reception response information on the data through a UL subframe of the second cell, wherein the relationship between the DL subframe and the UL subframe is determined by a parameter value set in a specific TDD UL-DL configuration, which is the TDD UL-DL configuration having the least number of DL subframes from TDD UL-DL configuration(s), in which subframes set as a DL in the first or second cell are all set as DLs.