A sorter for sorting sheets out is provided with a bin unit (15) including a plurality of bins (16) having specified length and width and a bin shifting (23,24) mechanism for shifting the bin unit (15) upward and downward. The respective bins (16) are vertically spaced apart and adapted for placing the sorted sheets thereon. The sorter is further provided with a first detector (218) for detecting that the bin unit (15) has been moved down to a home position region defined in a lower portion of the sorter, and a shift controller for controlling the bin shifting mechanism (23,24). The shift controller shifts the bin unit (15) downward until the first detector (218) conducts the detection when the bin unit is not in the home position region when the power is applied to the sorter. Accordingly, the home position of the bin unit (15) can be detected accurately with a simple structure. Additionally there are disclosed an openable sheet stopper and alignement means and an input and display device for the postprint processing unit.
