1. A banknote processing apparatus that performs an unfit note determination to determine degree of soiling of a banknote being transported, and sorts the banknote in accordance with a determination result, the banknote processing apparatus comprising: a banknote receiving unit that receives the banknote; a transport unit that transports the banknote received by the banknote receiving unit to one of plural output destination units in accordance with a result of an unfit note determination; an image acquiring unit that irradiates the banknote being transported by the transport unit with lights of plural wavelengths, and acquires images by irradiating the lights of respective wavelength as the images of plural image types; and an unfit note determining unit that performs the unfit note determination by correcting the image based on the wavelength of the light irradiated for acquiring the image.