The monitoring of slope deformations is often required for management of construction or for disaster prevention. Although various kinds of electrical monitoring systems have been developed, they still have problems on shielding electric noises, waterproofing and so on. An optical monitoring system is expected to solve those problems because it is basically unaffected by electric noises and waterproofed by itself. Borehole inclinometer is one of the typical transducers for slope deformation monitoring. By electrical ones, it is hard to take continuous data of many points in a small diameter borehole. To improve these weak points, we developed the monitoring system with borehole inclinometers using Fiber Bragg Gratings (FBG) as a strain sensor. The transducer consists of series of unit-bars connected each other with elastic joints. FBGs were embedded on the elastic joints, and bending angles of each joint were measured by FBGs. The transducer was set in a borehole, and underground deformations were measured as bend of each joint at a remote monitoring center. We had applied this monitoring system for artificial slope under construction for 4 months. The data obtained by the system indicate the deformation according to a progress of land banking.