A relaying device comprising: a communication unit (3, 33, 5) configured to communicate with a plurality of communication terminals (20, 22, 23, 24, 25, 26, 27, 28) that perform voice communication; a communication session processing unit comprising a mixing table the communication session processing unit being configured to, when one communication terminal (20, 22, 23, 24, 25, 26, 27, 28) has called another at least one communication terminal (20, 22, 23, 24, 25, 26, 27, 28), establish a communication session in which the communication terminal (20, 22, 23, 24, 25, 26, 27, 28) that has called and the at least one communication terminal (20, 22, 23, 24, 25, 26, 27, 28) that has been called are registered as participating terminals in the mixing table, and upon a voice signal being transmitted from a participating terminal in the established communication session, transmit this voice signal to another participating terminal in the same communication session, wherein the another participating terminal is determined by referring to the mixing table; and a communication monitoring unit configured to register a virtual device that is a virtual communication terminal as a participating terminal of the communication session in the mixing table, acquire a voice signal transmitted from the communication session processing unit to the virtual device, and record or reproduce the voice signal, wherein the communication monitoring unit associates the virtual device with a predetermined communication terminal (20, 22, 23, 24, 25, 26, 27, 28) or a predetermined group constituted by a plurality of communication terminals (20, 22, 23, 24, 25, 26, 27, 28), and if the communication terminal (20, 22, 23, 24, 25, 26, 27, 28) or group with which the virtual device is associated is registered as a participating terminal of the communication session in the mixing table, registers the virtual device as a participating terminal of the communication session. a communication unit (3, 33, 5) configured to communicate with a plurality of communication terminals (20, 22, 23, 24, 25, 26, 27, 28) that perform voice communication; a communication session processing unit comprising a mixing table the communication session processing unit being configured to, when one communication terminal (20, 22, 23, 24, 25, 26, 27, 28) has called another at least one communication terminal (20, 22, 23, 24, 25, 26, 27, 28), establish a communication session in which the communication terminal (20, 22, 23, 24, 25, 26, 27, 28) that has called and the at least one communication terminal (20, 22, 23, 24, 25, 26, 27, 28) that has been called are registered as participating terminals in the mixing table, and upon a voice signal being transmitted from a participating terminal in the established communication session, transmit this voice signal to another participating terminal in the same communication session, wherein the another participating terminal is determined by referring to the mixing table; and a communication monitoring unit configured to register a virtual device that is a virtual communication terminal as a participating terminal of the communication session in the mixing table, acquire a voice signal transmitted from the communication session processing unit to the virtual device, and record or reproduce the voice signal, wherein the communication monitoring unit associates the virtual device with a predetermined communication terminal (20, 22, 23, 24, 25, 26, 27, 28) or a predetermined group constituted by a plurality of communication terminals (20, 22, 23, 24, 25, 26, 27, 28), and if the communication terminal (20, 22, 23, 24, 25, 26, 27, 28) or group with which the virtual device is associated is registered as a participating terminal of the communication session in the mixing table, registers the virtual device as a participating terminal of the communication session.