The present invention relates to a wireless communication system and more specifically, to a method for supporting a basic service set (BSS) in a wireless LAN system and an apparatus therefor. According to one embodiment of the present invention, a method for supporting a BSS by an access point (AP) in a wireless LAN system can comprise the steps of: scanning an overlapping BSS (OBSS); and selecting a primary channel for a new BSS of the AP from channels for which a beacon is not detected during the OBSS scanning. The primary channel can be selected from all channels except the secondary channel of the OBSS. In addition, if the new BSS supports an operating channel having a 4 MHz, 8 MHz or 16 MHz channel bandwidth, a primary channel having a 2 MHz channel bandwidth can be chosen for the new BSS.