Route selecting method and node apparatus

A node apparatus calculates the arrival rate in a link, discretizes the calculated arrival rate according to thresholds that are set so that the intervals between thresholds in the range in which a large number of the arrival rates in the links with a high frequency of usage exist become narrower, and calculates the link cost according to the value after the discretization. The node apparatus then obtains, from adjacent node apparatuses, the route cost for each route to each final destination that may be reached, and integrates the obtained route cost by the calculated link cost to calculate the route cost to each final destination that can be reached from the local node apparatus via the adjacent node apparatus. The node apparatus then selects the adjacent node apparatus to be the transmission destination according to the route cost of the route to the final destination of a data frame.