Image reading apparatus, and image expansion and contraction correcting method

An image reading apparatus comprising:

• a plurality of conveying units configured to convey a document;
• a first image reading unit configured to read an image from a document in a stationary state on an original base plate, and to read an image from one surface of a document that is being conveyed by at least one of the plurality of conveying units, the first image reading unit being designed to be movable;
• and
• a second image reading unit configured to read an image from the other surface of the document being conveyed by at least one of the plurality of conveying units,
• wherein the first image reading unit moves while reading the image from the document being conveyed so that the relative speed between the first image reading unit and the document and the relative speed between the second image reading unit and the document become equal to each other, in accordance with a change in document conveying speed caused by the difference between a combination of the plurality of conveying units conveying the document during a reading operation performed by the first image reading unit and a combination of conveying units conveying the document during a reading operation performed by the second image reading unit.