Abstract: A method of setting terminal state and assigning ID number for stack network concentrators, and a device executing the method are provided. A terminal state setting is executed when a concentrator detects that there is no electric signal, through one of it's I/O ports, coming from its adjacent counterpart. A device for implementing such execution includes a first power source generator, a first power source detector, a second power source generator and a second power source detector. Steps for implementing the ID number assignment includes: a) causing two I/O ports of each concentrator in an open state, b) sequentially assigning distinctive ID numbers respectively for the concentrator, and simultaneously causing two I/O ports of the one concentrator having been assigned ID number in connecting state, and c) reiteratively executing step b) until all concentrators have been assigned ID numbers respectively.