According to an embodiment of present invention, a method for transmitting a coexistent data stream, the method including: transmitting coexistent data stream transmission information including transmission power information of a first data stream targeted for a first station and transmission power information of a second data stream targeted for a second station in an environment in which the first station, a legacy station, coexists with a second station, a station supporting a wireless local area network (WLAN) system evolved further than the first station; and transmitting, by an access point (AP), the first and second data streams to the second station and the first station, wherein the AP transmits the first data stream with a higher transmission power level than that of the second data stream according to the coexistent data stream transmission information.