A method of transmitting a frame in a Wireless Local Area Network (WLAN) system, and which includes receiving, by a first station, information about an association identifier (AID) from an access point, the AID identifying the first station in the WLAN system; transmitting, by the first station, a DLS request frame to a second station; receiving, by the first station, a DLS response frame from the second station; generating, by the first station, a PPDU including a VHT-SIG field and a PSDU; and transmitting, by the first station, the PPDU to the second station via the direct link. Further, the VHT-SIG field includes identity information indicating a partial AID that is formed from the AID of the second station and has a length shorter than the length of the AID of the second station.