To inspect the lining plate of a fuel storage pool without removing a fuel storage rack installed in the fuel storage pool.

This inspecting device is provided with an operation pole 12 inserted between the inner wall face of a fuel storage pool 1 and the outside face of a fuel storage rack 4 from above a platform 8, a sensor arm 14 bendably connected to the lower section of the operation pole 12 via a fulcrum 13, a sensor support 15 storing a sensor 16 traversably fitted to the sensor arm 14, a reference plate 24 and a needle 25 fitted to the upper section of the operation pole 12, first and second pulleys 19, 20 provided at the lower section of the operation pole 12, a third pulley 21 fitted to the tip section of the sensor arm 14, a first wire 26 connected with one end to the sensor support 15 through the first pulley 19 and connected with the other end to a monitor 11 provided on the platform 8 through the reference plate 24 and the needle 25, and a second wire 27 connected with one end to the sensor arm 14 through the pulley 20 and connected with the other end to the monitor 11. The sensor 16 is inserted along a lining plate 2 for an inspection.