A transmission method and device based on preamble puncturing in a wireless LAN system are disclosed. A method by which a first STA performs communication in a wireless LAN system, according to one embodiment of the present disclosure, comprises the steps of: receiving a first PPDU from a second STA; acquiring information related to at least one first punctured resource unit; and transmitting, in response to the first PPDU, to the second STA, a second PPDU based on at least one second punctured resource unit, wherein the at least one first punctured resource unit can be at least one part of the at least one second punctured resource unit.