A method and an apparatus for transmitting an EHT PPDU to a wireless LAN system are presented. Particularly, a transmission device generates an EHT PPDU, and transmits the EHT PPDU to a reception device through a 320 MHz band of which a partial band is punctured on the basis of an RF. A legacy preamble includes an L-STF and an L-LTF. The legacy preamble is generated by applying a first phase rotation value. The first phase rotation value is determined on the basis of a first method and a second method. The first method is for acquiring an optimum PAPR in the L-LTF. The second method is for acquiring an optimum PAPR on the basis of a maximum transmission bandwidth supported by the RF. The first phase rotation value is acquired on the basis of a second phase rotation value and a third rotation value. The second phase rotation value is a phase rotation value which repeats a phase rotation value that is defined with respect to an 80 MHz band in an 802.11ax system. The third phase rotation value is a phase rotation value that is defined by 80 MHz band units in the 320 MHz band.