A transmission device includes: a code generator configured to generate delay measurement information; an insertion unit configured to sequentially insert the delay measurement information generated by the code generator, in each of delay measurement signals in a plurality of frames, and to sequentially transmit the plurality of frames sequentially inserted with the delay measurement information to a counterpart device on a transmission path whose path delay time is to be measured; and a detector configured to receive a plurality of frames transmitted from the counterpart device and to detect the delay measurement information included in each of delay measurement signals in the plurality of received frames.