A source coil line-break/short-circuit detecting circuit and a probe connection detecting circuit are provided to the source coil driving circuit unit of an endoscope shape detecting apparatus. The source coil line-break/short-circuit detecting circuit detects line-breaks and short-circuits of the source coils. The probe connection detecting circuit detects whether a connection exists with a probe. A marker coil line-break/short-circuit detecting circuit detects line-breaks and short-circuits of the marker coils. A marker connection detecting circuit detects whether a connection exists with a marker. Accordingly, using the apparatus without being connected to a probe or markers can be avoided by detecting the connection of the probe and markers by the probe connection detecting circuit and marker connection detecting circuit, respectively, when the system is energized, thereby avoiding detecting noise and consequently displaying a random image on the monitor.