Sheet aligning device and image forming apparatus

A sheet aligning device comprising:

• a discharging unit that discharges a sheet in a first direction;
• a stacking unit that receives and stacks therein the sheet discharged by the discharging unit;
• an aligning unit that performs an alignment operation to align the sheet stacked in the stacking unit in a second direction perpendicular to the first direction;
• a detecting unit that detects a sheet position of either one of a first sheet placed at a top of a stack of sheets in the stacking unit and a second sheet placed just below the first sheet;
• and
• a controlling unit that controls an alignment position at which the aligning unit is to perform the alignment operation based on the sheet position detected by the detecting unit, the alignment position including a positional angle of the aligning unit.