Abstract: A cable branching unit which enables the exchange of signals through normal cables without suspending the power supply even when a short mode fault is caused in a cable branching from the cable branching unit. The cable branching unit branches a first cable into a second and a third cable and comprises a band pass filter for extracting a control signal multiplexed among signals transmitted from the first land station through the first cable, and a relay short circuits, to a ground, one or both of the cable connected to the second land station and the cable connected to the third land station, according to the control signal extracted by the band pass filter.