Patent ID: 7609399

Claim:
An original document reading device comprising: document setting unit means for receiving a plurality of sheets of a document; document feeding means for feeding the plurality of sheets of the document arranged in the document setting unit means one sheet at a time; both-sides reading means for reading an image of each side of the document fed by the document feeding means; front-back detecting means for detecting front and back sides of the document based on at least one of the images of each side of the document read by the both-sides reading means; and a means for detecting switching of a set in a document with a plurality of sets in response to detection of switching of the front and back sides of the document with the plurality of sets by the front-back detecting means in a process in which the document with the plurality of sets that has been stacked and arranged in the document setting unit means is fed one sheet at a time by the document feeding means and the image of each side is read by the both-sides reading means.