The accuracy for determining a fake finger in which a thin film is attached to a surface of a finger is improved. A fake-finger determination device includes an imaging unit 10 that images a reflected light image and a transmitted light image of an authentication object serving as a fingerprint authentication object, a classifying unit 31 that classifies each of the reflected light image and the transmitted light image into a foreground portion having a feature of a skin image and a background portion having no feature of a skin image, based on a hue value of a pixel included in each of the images, a detecting unit 32 that compares the foreground portion of one image of the reflected light image and the transmitted light image with the background portion of the other image to detect an overlapping portion, and a determining unit 33 that determines whether or not a foreign substance is present in the periphery of a finger using the overlapping portion.