Disclosed are a method and an apparatus for transmitting a downlink in a wireless communication system. A method for transmitting the downlink in a WLAN comprises the steps of: an access point (AP) transmitting, to a plurality of stations (STA), each of a plurality of request to send (RTS) frames through each of a plurality of channels; and the AP receiving a clear to send (CTS) frame from at least one of the plurality of STAs through at least one channel from the plurality of channels, wherein each of the plurality of RTS frames may include channel information for indicating a channel to be used from among the plurality of channels when transmitting the downlink to each of the STAs, and identifier information for indicating the plurality of STAs.