A foolproof device provided to a manufacturing process includes an imaging part that captures an object on which a plurality of identifiable marks are provided, an image processing part that obtains state data including a coordinate position of each mark from at least one captured image captured by the imaging part, a storage that stores reference data obtained by the image processing part, the reference data including a reference position of each mark, and a comparison processing part that compares the reference data stored in the storage with the current state data obtained by the image processing part, and outputs a result of the comparison regarding at least some of the plurality of marks.