Hierarchical routing is effective for large ad hoc networks. However, it is difficult to maintain the hierarchical structure for routing due to node movement. This paper proposes an adaptive method for maintaining the hierarchical structure. The features of the proposed method are (1) the roles of nodes for the hierarchical structure are changed depending on the status of nodes in the restricted vicinity, and (2) the cluster size is adjusted so that the number of nodes in each cluster is bounded by two constants. The adaptability of the proposed method has been evaluated by theoretical considerations and simulation experiments. The results show that node roles and clusters efficiently converges to stable states because of the features. The proposed method therefore has high adaptability to node movement.