It is an object to provide a communication terminal capable of determining a cluster formation so as to promptly perform addition of a participant terminal, while maintaining the quality of a stream relay path. Cluster monitoring terminal (430) is an apparatus to determine a cluster formation in a network performing packet transfer according to terminal relay-type multipoint communication, and includes: a cluster quality calculation section (432) for acquiring cluster quality representing a small loss in a packet to be received, per a cluster; a cluster sustainability calculation section (433) for acquiring cluster sustainability representing ease of acceptance of a participant terminal, per a cluster; and cluster division/integration analysis section (434) for determining cluster division with respect to a cluster having low cluster quality, and determining integration with other cluster with respect to a cluster having high cluster quality and low cluster sustainability.