A disclosed feature of the present specification is to provide a method for transmitting a hybrid automatic repeat request (HARQ) acknowledgement/negative-acknowledgement (ACK/NACK) signal using a sidelink. The method may comprise the steps of: receiving from a transmission terminal data in a first time section within a sidelink subframe n; and transmitting a HARQ ACK/NACK signal in a second time section within the sidelink subframe n. A gap may exist between the first time section and the second time section in the sidelink subframe n. The gap can be used for switching between reception and transmission.