1. A paper sorting apparatus, comprising: a scanning unit configured to scan an image printed on a paper; a printing ratio determining unit configured to determine a printing ratio as a ratio of an area of the printed image as scanned by the scanning unit to a whole area on the paper with the printed image thereon; a classification determining unit configured to determine a recycling classification of the paper based upon the printing ratio determined by the printing ratio determining unit; and a sorting assist unit configured to assist sorting of the paper in accordance with the recycling classification of the paper determined by the classification determining unit.