A method and a device for transmitting and receiving a PPDU on the basis of an FDD in a wireless LAN system are presented. Particularly, an AP transmits a trigger frame to a first STA and a second STA. The AP transmits a first downlink (DL) PPDU to the first STA on the basis of the trigger frame. The AP transmits a second DL PPDU to the second STA on the basis of the trigger frame. The AP receives a first uplink (UL) PPDU from the second STA on the basis of the trigger frame. The trigger frame includes bandwidth information of a primary channel and a secondary channel. The first DL PPDU is transmitted through the primary channel. The second DL PPDU and the first UL PPDU are transmitted through the secondary channel. The first and second DL PPDU are simultaneously transmitted. The first UL PPDU is received after a preset period after the second DL PPDU is transmitted.