Constructing a system capable of functioning without any human support over an extended period is the aim of many engineers. However it is generally considered to be difficult to make decentralized self-organizing autonomous system fault-tolerant. In this paper, we propose to apply the theory of highly structured self-diagnosable systems to this problem. As an example, we apply the theory and recursive procedures method of fault-tolerant system construction to a decentralized self-organizing autonomous robotic system that forms a circle. The result of simulation shows the usefulness of the proposed method. The highly structured self-diagnosable system has an O(|E|) fault-identification algorithm that can diagnose each of the units in the system independently, locally and in any order, where E and |E| mean the set of the directed edges and its cardinality, respectively.