The present invention is a transmission apparatus and a data communication channel processing method that make it possible to realize construction of a monitoring and controlling data communication network in accordance with a network management form desired by a user or an already existing network management form in a network conforming to SONET, SDH, etc., and the transmission apparatus is configured so as to comprise a data communication channel terminator for selectively performing termination processing of an signal received by a data communication channel in accordance with an area attribute setting and a data communication channel pass-through unit for passing through a signal for which termination processing is not performed by the data communication channel terminator to a transmission apparatus belonging to another area.