Proposed are a method and device for configuring a field for instructing the transmission of an A-PPDU in a wireless LAN system. Specifically, a reception STA receives an A-PPDU from a transmission STA. The reception STA decodes the A-PPDU. The A-PPDU includes an HE PPDU for a primary 160 MHz channel and an EHT PPDU for a secondary 160 MHz channel. The EHT PPDU includes first and second U-SIG fields. The first U-SIG field includes a UL/DL field. The second U-SIG field includes a PPDU type and compression mode field. When the value of the UL/DL field is set to 0 and the value of the PPDU type and compression mode field is set to 3, the PPDU type and compression mode field includes information for notifying that the A-PPDU has been transmitted, and the EHT PPDU is transmitted using DL MU OFDMA.