To provide a remote maintenance system in which an analog private line for a maintenance terminal is unnecessitated.

Primary group interfaces 13, 14 of a private branch exchange 11 at a remote side and a private branch exchange 12 at a local side allows m-bit of the remote maintenance information to be inserted and extracted to transmission and reception of multiframe information by being switched by multiplexes 171, 172 and decoders 201, 24. The maintenance terminal 18 for the private branch exchange 11 at the remove side transmits and receives a command to switch a maintenance terminal interface 21 of the private branch exchange 12 at the lockal side to the remote side to and from the private branch exchange at the lockal side as remote maintenance information, after the transmission and reception of the command, the remote maintenance of the private branch exchange 12 at the local side by the maintenance terminal 18 of the private branch exchange 11 at the remote side is performed by transmitting and receiving the remote maintenance information and when the remote maintenance completes, the command to return the maintenance of the private branch exchange at the local side to the local side is executed by transmitting and receiving the remote maintenance information.