Sounding method for beamforming transmission in wireless lan system, and apparatus therefor

Proposed is an access point (AP), which performs sounding to transmit a frame to one or more stations (STA) using a beamforming scheme in a wireless LAN system. The AP receives a beamforming feedback, which is generated on the basis of an operation in which the STA groups a predetermined number of tones according to a tone grouping element (Ng) and measures a predetermined signal transmitted by the AP, wherein Ng is set to be a multiple of 4.