[Problem] To provide a relaying device and a voice communication system with which calling and listening among a plurality of talk groups is possible.
[Solution] The relaying device is provided with: a relaying device which stores a plurality of groups and terminal devices belonging to each of the groups, and, when a voice signal is received from one or more of the terminal devices (calling terminal devices), transfers the voice signal to the terminal devices other than the calling terminal device in the group to which the calling terminal device belongs; and the plurality of terminal devices which are connected to the relay device over a communication network. The relaying device also stores the master-slave relationship among the plurality of groups, transfers the voice signal to the terminal devices belonging to a master group if the group to which the calling terminal device belongs is a slave group, and transfers the voice signal to the terminal devices belonging to slave groups if the group to which the calling terminal device belongs is the master group.