The invention comprises a step of constructing a plurality of groups using a plurality of wireless nodes during construction of a network; a step of provisionally deciding, from among the wireless nodes in each group, a group master node serving as a group master that communicates with the other nodes in the group and that functions as a communication relay station for communicating with the other groups, with the other nodes in the group serving as slave nodes that are connected under the control of the group master node to perform their respective terminal station operation; a step in which the wireless nodes in each group exchange data with each other at a commencement session and calculate the minimum required transmission power for each other; a step in which the wireless nodes in each group use the calculated minimum required transmission powers to communicate with each other; and a step of, when determining that the time of changing the group master has come, causing one of the slave nodes to take over the group master.