An acquisition means repeatedly acquires three-dimensional data of a monitoring target surface on a time axis. A deformation detection means detects, based on a plurality of pieces of the three-dimensional data, a first deformation occurring at a first time, and a second deformation occurring at a position different from an occurrence position of the first deformation at a second time being after the first time. A deformation prediction means predicts, based on a detection result by the deformation detection means, that a third deformation may occur in a future at a position different from occurrence positions of the first deformation and the second deformation.