A method and a device for transmitting a PPDU in a WLAN system are proposed. Specifically, an AP generates a PPDU and transmits the PPDU to a STA through a broadband. The PPDU includes an EHT-LTF and a data field. The data field includes a pilot tone. The coefficient of the pilot tone is set to a second pilot sequence in which a first pilot sequence is repeated. The first pilot sequence is {1 1 1 −1 −1 1 1 1}.