A sheet post-processing apparatus implements a tilted edge-binding process by a movable table rectilinearly driving portion that moves a stapling unit rectilinearly via a movable table, and rotating the stapling unit to drive a staple near a sheet corner when the staple is tilted at a predetermined angle with respect to a sheet-conveying direction. The sheet post-processing apparatus includes the movable-table rotationally driving portion that rotates the movable table to cause the stapling unit to tilt at a position to drive the staple at the predetermined angle with respect to the sheet-conveying direction, and a tilt retention portion that mechanically holds the movable table to maintain the stapling unit tilted.