PURPOSE: To make a bin effectively available without reducing the number of maximum copies being sortable, by installing plural units of detectors finding whether or not sheets are in the bin, while dividing the whole bin into plural groups.

CONSTITUTION: A sort mode is selected by a sort key, and when copy paper 3 does not exist in all bins 13, a control unit permits the sort action available for all bins with a signal out of bin sensors 27 and 28. And, setting the number of copies below 20 copies by means of a tenkey, when a print key is pressed, sheets of the copy paper 3 are discharged piece by piece to the corresponding bin from a first bin 13-1 in regular sequence. Likewise, when the number of set copies is less than ten sheets, if the sort key is pressed again after the sort action is over, a fact that a latter half 10 bin still remains unused is judged with a signal of the bin sensor 28 whereby the sort action from an 11th bin 13-11 downward is made to be attainable. Therefore, both the first half and the second half bins come repeatedly usable in regular order, thus these bins can be effectively available.