An image reading apparatus includes a document feeder, a reading unit configured to read an image of a document fed by the document feeder, a facing member positioned to face the reading unit via a document feeding path, and a detection processing unit configured to perform area detection processing for detecting an area of the document with respect to a read image obtained by the reading unit. The facing member includes a white portion and a gray portion. The reading unit selectively performs normal reading for reading the image of the document with the white portion of the facing member as a background and auto-crop reading for reading the image of the document with the gray portion of the facing member as the background. The detection processing unit performs the area detection processing only in the auto-crop reading.