A route monitor control system includes a plurality of OAM cell handlers (OCHs); a plurality of virtual path handlers (VPHs); a plurality of virtual channel handlers (VCHs); trunks; and a control unit. The control unit issues an OAM (operation and maintenance) cell send instruction to a specific one of the plurality of OAM cell handlers, and carries out a loop back control to at least one of the virtual path handler, the virtual channel handler, and the trunk, which are associated with the specific OAM cell handler, as an object unit in response to the OAM cell send instruction. Also, when the specific OAM cell handler sends out an OAM cell from the specific OAM cell handler to the object unit in response to the OAM cell send instruction, the control unit determines a fault position based on returning or non-returning of the OAM cell from the object unit to the specific OAM cell handler.