Sheet processing apparatus and image forming system

A sheet processing apparatus, comprising:

• a stacking section in which at least one sheet of paper conveyed from upstream is stacked;
• a first alignment section which aligns both end portions in a sheet conveyance direction of the sheet stacked in the stacking section;
• a second alignment section which aligns both end portions in a width direction, that is orthogonal to the sheet conveyance direction, of the sheet aligned by the first alignment section;
• a sheet ejection section which ejects the sheet stacked in the stacking section outside the stacking section;
• and
• a control section which moves a pair of horizontal alignment plates away from the both end portions in the width direction of the sheet after operating a gripping section so as to grip the sheet in a state where the pair of horizontal alignment plates contacts the both end portions in the width direction of the sheet supported by a supporting section,
• wherein
• the first alignment section includes:
• the supporting section which supports a lower end portion in the sheet conveyance direction of the sheet;
• and
• the gripping section which grips the sheet at a central portion in the width direction of the sheet supported by the supporting section, and
• the second alignment section includes the pair of horizontal alignment plates which is provided at positions facing each other to sandwich, along the width direction, the sheet supported by the supporting section and is moved along the width direction to contact and move away from the both end portions in the width direction of the sheet supported by the supporting section.