A clustering method of a wireless sensor network is provided to minimize energy consumption. The clustering method includes the operations of determining a number of initial nodes within radio range of ordinary node, the ordinary nodes existing within radio range of a cluster head, and setting an ordinary node having a highest number of initial nodes among the ordinary nodes in the radio range of the cluster head, as a gateway. Because the number of usually large energy consuming cluster heads and gateways can be minimized, energy efficiency of wireless sensor network increases.