Disclosed are a communication method and a communication device in a wireless LAN system that supports multi-bandwidth. The communication method in a wide-area wireless LAN system according to one embodiment of the invention comprises: a step in which a communication device of a network that supports multi-bandwidth generates a basic frame based on either a first bandwidth having the lowest signal-to-noise ratio from among preset bandwidths, or a second bandwidth the size of which is double that of the first bandwidth; a step in which the communication device configures a duplication mode frame based on the basic frame; and a step in which the communication device transmits the duplication mode frame over a plurality of bands.