The present invention relates to a method and an apparatus for transmitting an acknowledgment/negative-acknowledgement (ACK/NACK) of a terminal in a wireless communication system. More specifically, the method comprises the steps of: receiving a wide area network (WAN)-based downlink signal; and transmitting the ACK/NACK in accordance with first hybrid automatic repeat request (HARQ) processes, based on third wireless resources except for at least one second wireless resource for device-to-device (D2D) among first wireless resources for WAN communication, wherein the HARQ processes are characterized in that WAN uplink transmission timing on the second wireless resource is set up to be shifted to the third wireless resource.