Abstract: An image reading apparatus includes a transmission type projection screen capable of reading an image projected on an inner surface side of the projection screen from an outer surface side thereof, a projection optical system for projecting an image onto the inner surface side of the projection screen, and a reading unit movable in a projection optical path between the projection screen and the projection optical system for reading image information in an image reading mode. A light shield is capable of being moved to a position where an ambient light incident from the outer surface side of the projection screen, reflected by the projection optical system and entered into the reading unit, is blocked in the image reading mode.