An image reading apparatus for reading an image on an original document by irradiating it with light and photoelectrically converting reflected light from it by an image pickup unit, including: an original document guide member positionable opposite to the image pickup unit, with a conveyance position of the original document therebetween; a white reference member that is positionable, the same as the original document guide member, and has a reference white color; an achromatic constant-density reference member that is positionable, the same as the original document guide member, and has a reference achromatic constant-density; a drive unit that moves one of the three members so as to be positioned opposite to the image pickup unit; and a control unit that controls execution of detection processings for dust detection from data obtained by moving, as described above, the achromatic constant-density reference member and the white reference member by reading them.