To facilitate malfunction detection in laying of an optical composite cable.

This detecting apparatus has a loop back unit 10 which is connected to the connector of one end of an optical camera cable, and is composed of an optical loop fiber 11 connecting a first optical fiber 31 and a second optical fiber 32, and short-circuiting wiring conductors 12 short-circuiting the plurality of electric wires of the optical camera cable. Moreover, the apparatus comprises a measuring unit 40 which is connected to the connector of the other end of the optical camera cable, and is composed of a transmission loss measurement portion for measuring a transmission loss between the first optical fiber and the second optical fiber, a resistance measurement portion for measuring the resistance values between the electric wires, a disconnection detection portion for determining the existence of disconnection of each electric wire from the measured resistance values, and a display portion for displaying the measured transmission loss and results of disconnection detections by the disconnection detection portion.