An image forming apparatus having a device capable of identifying an image orientation to allow adequate processing to be executed and a device capable of binding sheets by determining a binding position. When an image orientation cannot be identified on the basis of a predetermined reference object, it is identified on the basis of another object. When the image orientation of a reference image and the image orientations of the other images are not coincident, an adequate procedure is executed to avoid an undesirable result. An orientation of a document image matching a predetermined adequate binding position is surely and accurately determined.