A layered channel access method of a Group Representative-station (GR-STA) in a Wireless Local Area Network (WLAN) system is provided. The method includes receiving a management, including setting information indicative of a first phase and a second phase frame, from an Access Point (AP), receiving a first radio frame from the AP or accessing a channel and sending a second radio frame to the AP during the first phase indicated by the setting information, and receiving a third radio frame from an affiliated STA of a group to which the GR-STA belongs or accessing a channel and sending a fourth radio frame to at least one STA of the group to which the GR-STA belongs during the second phase indicated by the setting information.