A wireless LAN system according to the present disclosure includes a wireless LAN base station (AP), and a plurality of wireless LAN terminals (STA) which perform uplink multi-user communication with the wireless LAN base station (AP). An AID indicating an associated wireless LAN terminal (STA) includes a specific bit generated by using a BCB. The wireless LAN base station (AP) and an unassociated wireless LAN terminal (STA) generate a UAID which indicates the unassociated wireless LAN terminal (STA) to include the specific bit or a processed bit obtained by processing the specific bit, and use a bit to be distinguished from the AID as a bit other than the specific bit of the UAID when the specific bit is included in the UAID.