Many schemes to reduce the inter-cluster handoff delay in wireless ATM networks have been proposed, but the previous schemes waste relatively large network resources to decrease the path rerouting delay. In this paper, we propose the 2-layered cluster concept, where the seamless inter-cluster handoff can be supported regardless of path rerouting time. As a result, the waste of wired resources and the rate of the inter-cluster handoff can be reduced. From the performance analysis and simulation, the inter-cluster handoff rate for non-real-time traffic is only about 1/3 of the conventional result. Such advantageous features of the proposed scheme neither incur any increase of the total handoff rate nor require additional ATM switches.