A communication terminal (6a, 6s, 6L) includes the following functional units. A relay communication establishment unit (621) establishes communication paths via respective relay devices (4a to 4N, 6p, 6q). A communication processing unit (624a) performs communication for pieces of divided data via the relay devices. A communication state monitor unit (622) changes a current set of the relay devices to a new set of relay devices so as to be used for the communication, based on estimation results of communication states.