A sorter for sorting copy sheets which are produced by a copying machine from an original document includes a plurality of trays which are vertically arranged in multiple stages at predetermined intervals and an indexer for selecting a tray from the plurality of trays to which an individual copy sheet is to be conveyed. The indexer includes a first roller which changes a direction of conveyance of the copy sheets, and the first roller curves the copy sheets upward so that ends of the upwardly curved copy sheets curve downwardly with respect to a bottom surface of the trays, thereby increasing the number of copy sheets which can be stacked in the trays and preventing the occurrence of paper jams.