A transmission device includes: a signal receiving part configured to receive a time division multiplexing signal in which a plurality of packets are stored; a separating part configured to separate the plurality of packets from the time division multiplexing signal; an assigning part configured to assign an identifier corresponding to a stored position in the time division multiplexing signal to each of the plurality of packets; and a packet transmitting part configured to transmit at least two packets having different identifiers out of the plurality of packets through a common transmission path.