A data transmission method of a station (STA) device in a wireless LAN system is disclosed. The data transmission method of an STA device, according to the present invention, comprises: a receiving step of receiving an uplink data frame from a first STA, wherein the uplink data frame includes first receiving operating mode information indicating a receiving operating mode to be changed by the first STA; and a transmitting step of transmitting an ACK frame for the uplink data frame, wherein the ACK frame includes mode change acceptance information indicating whether to accept or reject the change in the receiving operating mode according to the receiving operating mode information.