[Problem] To provide am audio communication system configured such that a relaying device and terminal devices are connected via a communication network, and communication between terminal devices is managed on the relying device side on the basis of the priority of communications.[Solution] The relaying device is provided with a network communication unit, a control unit, and a priority information storage unit. A network communication unit communicates with a plurality of terminal devices via a communication network. A control unit transfers audio signals between terminal devices participating in a communication session. When a calling audio signal specifying a terminal device participating in the existing communication session as a communication partner is received, and the priority of the new communication session is higher than the existing communication session, the control unit causes the terminal device participating in the existing communication session to participate in the new communication session. The terminal devices transmit, to the relaying device, the audio signals to which transferring destination information indicating the transferring information of the audio signal has been applied.