Disclosed is a wireless LAN system comprising: a memory; a central processing unit segmenting data, which is to be transferred, into frames, generating descriptors containing frame addresses and lengths in the memory, and storing the segmented frames and the descriptors into the memory in accordance with transmission priorities; a media accessing controller calling the frames of data, which is to be transferred, from the memory with reference to the transmission priorities and the descriptors, and temporarily storing the frames; and a transmitter transferring the frames stored in the media accessing controller. It is possible to improve data transmission speed and control facility, satisfying the quality of service for a standard of communication protocol.