A method of indicating destination stations, performed by an access point (AP), in a wireless local area network (WLAN) system supporting multi-user multiple input multiple output (MU-MIMO) is provided. The method includes transmitting a sounding request frame to the plurality of destination stations to transmit a sounding frame used for channel estimation between the AP and each destination station, receiving the sounding frame in response to the sounding frame request from each station, and transmitting a first data frame spatially multiplexed with respect to the plurality of destination stations by performing channel estimation on the basis of the sounding frame, wherein the sounding request frame comprises a group identifier (ID) indicating the plurality of destination stations.