To provide an image reading apparatus capable of easily acquiring proper shading for excellently reading an image even when part of an outer circumferential face of a shading roller gets dirt.

The image reading apparatus 100 is provided with: a discrimination means for discriminating the presence of dirt in a read region on the basis of read data acquired by an image read means 3 for reading an image of the read region corresponding to one or more main scanning lines on an outer circumferential face of a shading roller 10; and a control means for storing the read data of the read region to a memory 38 as shading correction data S when the discrimination means discriminates that no dirt exists in the read region and allows the image read means 3 to read an image of a read region different from the read region above by turning the shading roller 10 by a prescribed angle when the control means discriminates that the read region gets dirt.