PURPOSE: To improve a general-purpose property of a sorter by detecting a speed of conveyance of a copying sheet in a copying machine, and making adjustable the speed of conveyance of the copying sheet in the sorter based on said detected signal.

CONSTITUTION: A sorter 1 mounted on a copying machine 2 adjoining thereto has a plurality of bins 7 and an emergency tray 8, said copying machine receiving a copying sheet 4 discharged therefrom by means of a paper discharge roller 5. The sorter 1 further has a conveyor part comprising a conveyor belt 10 guiding a sheet 4 discharged from the copying machine 2 via a guide plate 9 and a conveyance roller 11 for driving said conveyor belt, etc., the conveyance roller 11 being driven by a pulse motor 13 via a transmission mechanism 12. Thereupon, each of controllers in the sorter 1 and the copying machine 2 are connected with each other via an I/O expander, whereby said pulse motor 13 is constructed to permit a speed of conveying the sheet in the sorter 1 to correspond to that in the copying machine 2.