An image reading device including (1) a transparent member having an image reading area, (2) a line sensor that moves in a line sensor moving direction, which is perpendicular to a reading line direction of the line sensor, (3) a first supporting structure that supports, at opposite ends of the image reading area in the line sensor moving direction, the transparent member such that the transparent member is not deformed with respect to the reading line direction when an external force is applied to the transparent member, and (4) a second supporting structure that supports, at opposite ends of the image reading area in the reading line direction, the transparent member such that the transparent member is movable between a first posture, where the transparent member is in a flat plate shape, and a second posture, where the transparent member is bent with respect to the line sensor moving direction.