A card identifying apparatus according to one embodiment of the invention has a light-receiving portion that reads a card on a pixel basis of a predetermined area as a unit including color information having brightness, RAM that stores image data comprised of a plurality of pixels read by the light-receiving portion, an image data thinning processing section that makes the number of read pixels lower in another direction than in one direction to vary the number of pixels of the image data when the reading means reads the card, and an judgment processing section that identifies authentication of the card based on the image data varied by the image data thinning processing section.