A load balancing method for a wireless local area network (LAN) which has a plurality of access points is provided in the present invention. The load balancing decision is made by a load balancing module according to traffic conditions and bandwidth availability of each traffic priority class based on a corresponding class of service. The load balancing module is a centralized module which the load balancing decision is determined by the centralized module, or is determined through information exchanges among distributed load balancing modules of the access points. The load balancing decision also takes into consideration of VLANs per VLAN tag basis. Each of the VLANs is defined with the corresponding traffic priority class.