The present invention relates to a wireless communication system, and more specifically, disclosed are a method and an apparatus for accessing a channel in a WLAN system. The method for accessing a channel from a station (STA) in a wireless communication system, according to one embodiment of the present invention, comprises the steps of: receiving from an access point (AP) a first frame including a traffic indication map (TIM) and a restricted access window (RAW) parameter set component; determining a RAW in which channel access of the STA is permitted, on the basis of the RAW parameter set (RPS) component; and transmitting a second frame to the AP from within the RAW that is determined, wherein the RAW includes at least one slot, the RPS component includes at least one RAW allocation field, each of the at least one RAW allocation field includes a RAW duration field and a slot duration field, and wherein an index of a slot which is allocated to the STA can be determined on the basis of an association identifier (AID) of the STA and the number of the slots in the RAW.