A method in which a terminal performs a HARQ operation in a NoMA-based system comprises a step of receiving a downlink control information (dci) format comprising a multiple access (MA) signature field for supporting NoMA transmission; a step of receiving downlink data based on a value of the MA signature indicated by the MA signature field; and a step of transmitting an ACK/NACK signal with respect to the downlink data based on a subframe offset value, a frequency offset value, or a sequence index value, which are tied with the indicated value of the MA signature according to a predefined rule, wherein the subframe offset value comprises the subframe offset value between a reception subframe of the downlink data and a downlink HARQ feedback transmission subframe with respect to the downlink data, and wherein the frequency offset value indicates a frequency band used for transmitting the ACK/NACK signal.