PURPOSE: To provide a sheet stacking device which orderly stacks cut sheets carried by a conveyor into a stacking.

CONSTITUTION: Cut sheets 25 carried by a conveyor 20 are clamped by means of a clasp device 30, slowed down and fed into a stacking 16. When the quantity of the sheets to be stacked in the stacking reaches the specified value, an supplementary fork is inserted, and the stacking is rapidly lowered, and at the same time, a main fork is inserted. The supplementary fork is drawn out and another stacking is set while cut sheets are stacked on the main fork.