An image scanning device includes a placement-area image data capturing unit that captures placement-area image data corresponding to an area where documents are placed on a platen, a document image data capturing unit that captures pieces of document image data, each of which corresponds to one of the documents, and acquires positions of the pieces of document image data, in accordance with the placement-area image data captured by the placement-area image data capturing unit, a placement order acquiring unit that acquires an order in which the documents, each of which corresponds to one of the pieces of document image data, have been placed in accordance with at least the positions of the pieces of document image data, each of which corresponds to one of the documents, and a sequencing unit that assigns to the pieces of document image data the order acquired by the placement order acquiring unit.