Abstract: A conveyance device 4 for conveying a manuscript to an image reading section of a main body mounted by an image processing system is provided with a base member 6 removably fixed to the main body to provide a conveyance path 5, a driving mechanism and a manuscript guide member 8 for driving and conveying the manuscript. The manuscript is located between the manuscript guide member and a rib 9 at a left-hand side, and conveyed in a stable status. On a surface of a top end of a moving member 16 associated with the manuscript guide member is provided a white colored plate 17. A groove portion 18 other than the plate is dark, and the image is read to be binary coded whereby a pixel corresponding to the plate indicates "1". A position of the plate is located in the guide member or a right hand side edge of the manuscript, and a left hand side edge is fixed by the rib. Accordingly, a manuscript width (read width) Is determined from the pixel "1".