A sorting apparatus of linkage type, which sorts a plurality of recorded sheets which are ejected from an image forming apparatus. The apparatus has at least two sorters, a plurality of bins and a stapling unit in each sorter respectively to store a stack of recorded sheets sorted as a copy set and to staple each stack of recorded sheets and guide means to guide each recorded sheet to a bin of a sorter allocated by controlling means. The controlling means selects at least two sorters for making the copy sets larger in number then a predetermined number. The second sorter receives sheets even though some trays of the first sorter are left unused.