Abstract: In image reading apparatus, reading control portion causes image reading portion to read at least line of image data when pivoting angle of cover member with respect to document sheet table has changed from angle exceeding predetermined detection angle to angle equal to or less than detection angle. Photoelectric conversion portion is disposed in area that is out of predetermined maximum readable size area in image reading portion, and is covered by cover member when cover member is closed. Data correcting portion corrects image data read by reading control portion, based on output of photoelectric conversion portion output when pivoting angle has changed from angle exceeding detection angle to angle that is equal to or less than detection angle. Document sheet width detecting portion detects width, in main scanning direction, of document sheet placed on document sheet mounting surface, based on image data corrected by data correcting portion.