The present invention relates to a wireless communication system, and specifically, to a method and a device for the method which comprises the steps of: receiving a PDCCH including uplink scheduling information; and transmitting, at a UL SF, a PUSCH indicated by the uplink scheduling information, wherein, if the PDCCH requests a transmission of an ACK, the PUSCH includes ACK information about a SF set corresponding to the UL SF, wherein the SF set includes a plurality of SFs.