Disclosed, according to various embodiments, are a method for transmitting data by means of a first user equipment (UE) in a wireless communication system supporting a sidelink, and a device therefor. Disclosed are a method for transmitting data by means of a first UE, and a device therefor, wherein the method comprises the steps of: transmitting a first set of data to a second UE through a first link; receiving a first message requesting a beam search; and transmitting a second set of data through a second link formed on the basis of the first message, wherein the first UE, upon suspension of transmission of the first set of data for forming the second link, transmits a third set of data, which is a retransmission of the first set of data, after completion of the transmission of the second set of data, and wherein the third set of data has configured therein a second redundancy version (RV) which is different from a first RV configured in the first set of data.