Disclosed is a method by which an operating station (STA) transmits a signal in a multiple user (MU) scheme in a wireless LAN (WLAN) system. In the present method, the STA configures a wireless frame, which includes a data field for data transmission and a signaling (SIG) field including control information, wherein the SIG field includes a SIG A field, which includes bandwidth information indicating the whole bandwidth having a bandwidth of 2n times that of 20 MHz, and a SIG B field, which includes user specific information. Here, the bandwidth information of the SIG A field additionally indicates whether the whole bandwidth includes one or more 20 MHz bands (null channel), which are not used in the data transmission.