A transmission device includes at least one port, first and second transceivers, and a processor. The first transceiver transmits or receives a frame signal to or from one adjacent node within a ring network including a plurality of nodes. The frame signal includes an overhead and a plurality of slots. The second transceiver transmits or receives a frame signal to or from another adjacent node within the ring network. The processor sets port information to the overhead of a frame signal to be transmitted from the first transceiver. The processor acquires slot information from the overhead of a frame signal received by the first transceiver or the second transceiver based on the port information. The processor sets a received data signal in a slot allocated based on the slot information, among the plurality of slots of a frame signal to be transmitted from the first transceiver or the second transceiver.