Paper stacking device and image forming system

A paper stacking device comprising:

• a stacker on which paper is stacked;
• a paper ejector that ejects the paper toward the stacker;
• an aligning plate that is provided on a side of the paper stacked on the stacker, and aligns a side end of the paper;
• a paper floating member that is provided in the aligning plate, and supports, from below, the side end of the paper ejected from the paper ejector;
• and
• a blower that is provided on the side of the paper across the aligning plate, and blows air,
• wherein the aligning plate includes a blowing opening through which air from the blower is blown to the side end of the paper,
• the paper floating member is switched between:
• a paper floating position that advances from a side of the side end of the paper to an ejection mute of the paper, and causes the paper ejected from the paper ejector to float from uppermost paper stacked on the stacker;
• and
• a retreat position that retreats from the ejection route,
• when the paper floating member is located in the paper floating position, the blowing opening is opened, and
• when the paper floating member is located in the retreat position, the blowing opening is shielded.