To provide a sloping-land collapse detection system for detecting a landslide, a mudslide, etc. in a sloping land, so-called phenomenon of sloping land collapse.

Into the slope of a sloping land, a plurality of poles having predetermined curvature portions are driven, and an optical fiber is arranged along the poles. From the optical fiber, signal light in accordance with external force is outputted with respect to inputted reference light. The optical fiber bends locally since the poles move, when a collapse phenomenon occurs in the sloping land, and the output of the signal light to be outputted changes. A detection part connected to the optical fiber judges that a collapse occurs in the sloping land, when the variation width of the output from the optical fiber exceeds a preset threshold.