A method for performing, by a first device, wireless communication and an apparatus for supporting same are provided. The method includes: receiving a physical sidelink shared channel (PSSCH) from a second device; determining a physical sidelink feedback channel (PSFCH) resource associated with the PSSCH; and transmitting, to the second device, a hybrid automatic repeat request (HARQ) feedback on the PSFCH resource. Here, at least one subchannel for the PSSCH is associated with at least one first PSFCH resource including at least one second PSFCH resource, each second PSFCH resource included in the at least one first PSFCH resource is associated with each slot on the at least one subchannel, and the PSFCH resource may be determined on the basis of information related to the at least one subchannel for the PSSCH, information related to at least one slot for the PSSCH, and a source ID of the second device.