Huang and Wu in [IEEE Transactions on Computers 46 (1997), pp. 484-490] introduced the balanced hypercube BH n as an interconnection network topology for computing systems. In this paper, we completely determine the full automorphism group of the balanced hypercube. Applying this, we first show that the n-dimensional balanced hypercube BH n is arc-transitive but not 2-arc-transitive whenever n ≥ 2. Then, we show that BH n is a lexicographic product of an n-valent graph X n and the null graph with two vertices, where X n is a Z n−1 2 -regular cover of the n-dimensional hypercube Q n .