In wireless sensor networks, it is useful to construct a tree communication network topology in order to effectively collect sensed data from sensor nodes at a sink node. In the tree, the sink node should be a root node, and all the data sensed in the sensor nodes are transferred to the sink node using the tree connections. Compared to other topologies such as the mesh and random topologies, the tree topology does not request any routing protocols because each route from a sensor node to the sink node is uniquely decided after the tree structure is constructed. In this paper, we propose an autonomous algorithm for tree creation and its maintenance. It can extend the lifetime of the sensor network and support efficient data aggregation by balancing the communication tree structure automatically. Moreover, our algorithm simply manages all the involved sensor nodes and creates a tree structure by using them. Thus, this algorithm can be applied to actual sensor networks along with other algorithms or protocols. After describing the algorithm, some experimental results are shown to prove its effectiveness and robustness.