An apparatus includes: a light source opposite to one surface of a medium; a backing member opposite to another surface of the medium and including a backing surface opposite to the another surface of the medium; an imaging unit opposite to the one surface of the medium and at a position different from the light source in a conveyance direction, and to pick up an image of the medium and the backing surface on which a shadow of the medium is formed due to light from the light source; and a processor to generate image data including the image of the medium and the backing surface based on a result by the imaging unit, wherein the backing surface is inclined with respect to the conveyance direction, and a gap between the path and the backing surface decreases from a light source side toward an imaging unit side.