PURPOSE: To read a satisfactory picture at a high speed by providing a white reference plate in a place other than a stop claw and performing stable shading correction without being affected by the motion of the stop claw.

CONSTITUTION: A document reader 20 carries a document onto a contact glass 21 from a document table 1 by a carrying belt 11 and is provided with an automatic document feeder 20 which positions the document by a stop claw 16 at the time of subscanning, and a white reference plate 28 for shading is arranged on the outside of the effective picture range of the contact glass 21 on the side opposite to the set position of the stop claw 16.