An image reading apparatus and an image expansion and contraction correcting method are provided that improve the quality of each read image by restraining image expansion and contraction caused by a variation in the combination of conveying units for conveying each document. The image reading apparatus has conveying units (a first conveying unit, a second conveying unit, and a third conveying unit) that convey each document, and an image reading unit (a first image reading unit and a second image reading unit) that reads an image of each document being conveyed by the conveying units. The image reading speed of the image reading unit is adjusted in accordance with a change in the combination of conveying units that are conveying a document, so as to correct image expansion and contraction caused by a change in document conveying speed caused by the change in the combination of conveying units.