A sheet sorting apparatus includes a discharge port through which sheets are discharged, a stacking tray on which the sheets discharged from the discharge port are stacked, a sheet sorting member provided on a stacking surface on which the sheets of the stacking tray are stacked, and an operation mechanism for operating the sheet sorting member. The sheet sorting member is provided to be able to rise from the stacking surface by employing one end of the sheet sorting member as a pivot point, at a position at which the sheets fall from the discharge port. The sheet sorting member rises from the stacking surface by the operation mechanism, thereby forming an inclined surface, guiding the sheets placed on the inclined surface along the inclined surface, and shifting the sheets stacked on the stacking tray to a discharge direction of the sheets and a direction perpendicular to the discharge direction.

A sheet processing apparatus includes a shift unit including a pair of first conveying rollers that nip and convey a sheet and being able to move in a width direction orthogonal to a conveyance direction of the sheet in a state of nipping the sheet; a drive gear configured to transmit a driving force from a drive motor; a rack gear including a rack portion that meshes with the drive gear, the rack gear being configured to receive the driving force from the drive gear via the rack portion and, thereby, move the shift unit in the width direction in a state of nipping the sheet with a pair of first conveying rollers; a guide member configured to guide movement of the shift unit in the width direction; and a supporting member configured to nip the rack gear between the supporting member and the drive gear and support the rack gear, in which the rack gear is rotatable with respect to the shift unit on a plane parallel to the conveyance direction and the width direction.