The present invention relates to a wireless communication system and, in particular, to a method and an apparatus therefor, the method comprising the steps of: transmitting a random access request message including RAP transmission and PUSCH transmission, wherein the PUSCH transmission is transmitted using a resource related to the RAP transmission, and includes a C-RNTI; and in order to receive a response to the random access request message, monitoring a PDCCH in a time window, wherein a first PDCCH, accompanied by a TA command, is detected in the time window, and when the first PDCCH is indicated by the C-RNTI, a step of receiving the response to the random access request message is terminated.