A communication terminal device has circuitry configured to: judge, based on received information, whether or not source of the received information is intra-group communication destination; monitor whether or not the intra-group communication destination is the master unit based on the judgement; acquire the judging criterion information of the intra-group communication destination detected as the master unit; and switch, while the self device is operating by a master unit operation mode and when the other master unit is detected by monitoring, a master unit operation mode of the self device to a slave unit operation mode based on the judging criterion information of the self device and the judging criterion information of the other master unit.