A communication node includes: a routing information storing unit configured to store, as routing information, node information indicating a succeeding node and a preceding node in a ring network using a distributed hash table; and a routing information updating unit configured to update the node information, wherein when the succeeding node becomes inaccessible, the routing information updating unit acquires node information from one predetermined node accessible on the network at all times, determines, based on the acquired node information, whether the node that has supplied the node information satisfies a determination criterion for becoming its succeeding node, and designates the node that has supplied the node information as its succeeding node if the determination criterion is satisfied, while acquires node information from the preceding node indicated by the acquired node information if the determination criterion is not satisfied, and determines whether the node that has supplied the node information satisfies the determination criterion.