Disclosed are a method and an apparatus for operating based on a power save mode in a wireless LAN. The method for operating based on the power save mode in a wireless LAN may comprise the steps of: switching an STA from a sleep mode to an active mode after the STA has been switched to a power save mode based on a listen interval, to receive a first beacon frame transmitted by an AP; monitoring a frame for the STA transmitted by the AP until a timer started when the STA is switched to the active mode expires, when the first beacon frame indicates data buffered for the STA; and switching the STA to the sleep mode after the timer expires, wherein the timer can be reset when the frame is transmitted.