Provided is a sector discovery apparatus and method, the method including setting, by an AP in a WLAN system, an omni-beacon interval for transmitting an omnidirectional beacon and sector beacon intervals for transmitting a sector beacon with respect to one of a plurality of sectors which are spatially divided, transmitting the sector beacon to a current sector among the plurality of sectors, transmitting, to the current sector, a transmission frame indicating sectorized transmission or a transmission frame indicating omnidirectional transmission, in a sector interval between the sector beacon intervals, and receiving, from a terminal located in the current sector, a response frame indicating an association performed by receiving the transmission frame indicating the sectorized transmission.