To provide an inspection apparatus for the changed state of a tunnel, by which the changed state of the wall surface of the tunnel can be inspected automatically.

Image data obtained by photographing a prescribed surface change state on the proper wall surface of a tunnel in advance is input to an image processing part 3, the envelope component of a spatial frequency spectrum in an image is registered as a reference parameter, and the envelope component of a spatial frequency spectrum in an image obtained by photographing the wall surface of the tunnel 4 in the inspection of an actual changed state is found as a feature parameter. When the feature parameter is compared with the reference parameter, a face changed state which exists on the wall surface of the tunnel 4 is discriminated.