Proposed are a method and an apparatus for receiving a PPDU in a wireless LAN system. Specifically, a reception STA receives a PPDU from a transmission STA through a first band, and decodes the PPDU. The PPDU includes a preamble and a data field. The first band includes first to fourth sub-blocks. The data field includes first data for first and second sub-blocks and second data for third and fourth sub-blocks. The second data is generated on the basis of data obtaining by duplicating the first data and applying phase rotation to the third sub-block.