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: an STA receiving, from an AP, a beacon frame from a beacon frame time resource for the beacon frame, wherein a TIM included in the beacon frame indicates pending downlink data for the STA; the STA maintaining a sleep mode after receiving the beacon frame and until a monitoring start time resource for the downlink frame for delivering downlink data; and the STA receiving, from the AP, the downlink frame from a listen window including the monitoring start time resource.