An association method in a wireless LAN system using multiple channels includes: broadcasting a beacon frame including first channel information which is information on first available frequency channels of an access point; receiving an association request frame from a wireless station having received the beacon frame, the association request frame including the second channel information which is information on second available frequency channels of the wireless station among the first available frequency channels; and transmitting an association response frame to the wireless station, the association response frame including third channel information which is information on frequency channel allocated to the wireless station.