An adaptive routing system is used for a packet transmission network in which information in sent together with the address data and the data on the length of information. In this system, a number of nodes equipped with several input and output ports are distributed and connected by input links and output links. In this system, a neuron is allotted to each of the input and output ports of each node by the network and the network state is inputted to the neuron in order to make it possible to evaluate the traffic state of the network. In the equilibriumm state where the output of each neuron device does not change, the output port to which the neuron device having an output '1' is allotted is decided from among the neuron devices allotted to the outputs ports of each note and that output is determined as the most optimum output direction of the packet from each node.
