Disclosed is a sheet stacking apparatus which includes: a leading-edge regulating member configured to be positionally adjustable depending on a length of a plurality of corrugated paperboard sheets; a sheet stopper installed in the leading-edge regulating member in such a manner as to be movable with respect to a contact surface of the leading-edge regulating member reciprocatingly between a first position and a second position, and contactable with a leading edge of the corrugated paperboard sheet to be stacked in the hopper section; a detection section disposed upstream of the hopper section, and configured to detect a passing of each of the corrugated paperboard sheets; and a synchronization control device configured to reciprocatingly move the sheet stopper according to a detection signal, in such a manner as to allow the leading edge of the corrugated paperboard sheet to come into contact with the sheet stopper.