A channel access method in WLAN system is provided. The method includes receiving packets transmitted from a higher protocol layer, classifying the packets to map the packets to ACs to which the packets correspond, transmitting the packets to queues corresponding to the ACs to which the packets are mapped, among a plurality of queues by ACs, independently applying a channel access function to each of the plurality of queues by ACs by avoiding a collision among the plurality of queues by ACs, transmitting a packet determined to be transmitted first, according to the application result of the channel access function. The packet includes a first frame to be transmitted to a first terminal and a second frame to be transmitted to a second terminal. The plurality of queues by ACs are queues with respect to the first frame to be transmitted to the first terminal.