A method and apparatus for transmitting an EHT PPDU in a wireless LAN system is proposed. Specifically, a transmitting STA generates an EHT PPDU including a STF signal. The transmitting STA transmits the EHT PPDU to a receiving STA. The STF signal is generated on the basis of an EHT STF sequence for a 320 MHz band or a 160+160 MHz band. The EHT STF sequence for the 320 MHz band is a first sequence in which a predetermined M sequence is repeated, which is defined as {M 1 M 1 M 1 −M 0 M 1 −M 1 −M 1 M 0 M 1 M 1 M 1 −M 0 −M −1 M −1 M −1 −M}*(1+j)/sqrt(2). The sqrt( ) represents the square root. The predetermined M sequence is defined as M={−1, −1, −1, 1, 1, 1, −1, 1, 1, 1, −1, 1, 1, −1, 1}.