One embodiment of the present specification provides a method by which a wireless device manages a buffer for performing soft combining. The method can comprise the steps of: decoding data received through device-to-device (D2D) communication; determining whether an error exists in the decoded data; determining whether a radio resource control (RRC) connection with a base station is established or/and a carrier aggregation is configured and activated if the error exists; taking at least one from among an instantaneous buffer to be used when the carrier aggregation is activated and a hybrid automatic repeat request (HARQ) buffer to be used when the RRC connection is established, on the basis of whether the RRC connection with the base station is established and whether the carrier aggregation is activated; and storing, in the taken one or more buffers, a soft bit for performing soft combining.