Sheet processing apparatus and image forming apparatus

An image forming apparatus comprising:

• an image forming portion which forms an image on a sheet;
• and
• the sheet processing apparatus which processes the sheet on which the image is formed by the image forming portion, the sheet processing apparatus including:
• a conveyance portion which conveys the sheet;
• a stacking portion on which the sheet conveyed by the conveyance portion is stacked;
• an alignment reference member on which end portions, in a width direction perpendicular to a sheet conveyance direction of the conveyance portion, of the sheets conveyed to the stacking portion are abutted to align the sheets;
• an alignment member which is (i) moved from a first standby position toward the alignment reference member to align a first-size sheet having a first length in the width direction, and (2) moved from a second standby position, which is closer to the alignment reference member than the first standby position, toward the alignment reference member to align a second-size sheet having a second length in the width direction smaller than the first length in the width direction;
• a stapler which performs a stapling process of stapling the sheets with a staple having two staple legs;
• and
• a controller which controls movement of the alignment member,
• wherein the controller controls the movement of the alignment member based on information that the sheets to be aligned are the first-size sheets so that the alignment member is moved to align the first-size sheets from the first standby position toward the alignment reference member by a distance which, even if the sheet conveyed to the stacking portion is the second-size sheet, allows the stapler to staple the sheets moved by the alignment member with at least one of the two staple legs.