1. An image-reading apparatus comprising: a camera configured to scan one or more documents; a control unit configured to: cause the camera to scan one or more documents to acquire a read image; detect edge coordinates of a document image closest to an outer edge of the read image in a plurality of certain directions; and regionally divide the read image in the certain directions based on any one or both of a region of the read image in which no edge coordinates are detected and the edge coordinates of an edge end of the document image, wherein when the document image is contained in a divided region regionally divided by the control unit, the control unit acquires the read image excluding the divided region as a new read image and detects edge coordinates of a document image closest to the outer edge of the divided region in a plurality of certain directions in the new read image; a sheet sensor configured to detect a reading state of the document, wherein the control unit is configured to cause the camera to read one or more documents and acquire the read image when the sheet sensor detects that no document is present at a conveying inlet, and wherein the control unit is further configured to determine a missing image when the sheet sensor detects the document at the conveying inlet.