A method and an apparatus for transmitting a PPDU on the basis of an S-TDMA in a wireless LAN system are presented. Particularly, an AP transmits a trigger frame to a first STA and a second STA. The AP receives, on the basis of the trigger frame, a first trigger-based frame from the first STA and a second trigger-based frame from the second STA. The trigger frame includes a common information field and a user information field. The common information field includes S-TDMA indication information enabling the S-TDMA to be performed. The user information field includes: allocation information on a first RU to which the first trigger-based frame and the second trigger-based frame are transmitted; first symbol offset information on the first trigger-based frame; and second symbol offset information on the second trigger-based frame.