Disclosed are a method and a device for performing HARQ in a multiple antenna system. A terminal transmits uplink data via a plurality of antennas and through a Physical Uplink Shared Channel (PUSCH), and receives an ACK/NACK (Acknowledgement/Non-Acknowledgement) signal indicating whether or not the uplink data has been received, the signal being received via the plurality of antennas and through a PHICH (Physical Hybrid-ARQ Indicator Channel) which corresponds to the PUSCH. A downlink resource to which the PHICH is mapped is determined on the basis of the index (IPRB—RAlowest—index) of the smallest Physical Resource Block (PRB) among the PRBs to which the PUSCH is mapped, uplink DMRS (Demodulation Reference Signal) cyclic shift parameters (nDMRS) and Orthogonal Code Cover (OCC) index.