In the control of a cutting mechanism of a sheet processing apparatus, when rear end cut region (Sr) of a sheet is finely cut and divided into predetermined fine-cutting unit length (Lr0), the control section is configured to control the driving sources so that sheet conveying direction length (Lr1) of rearmost end divided region (Sr1) in rear end cut region (Sr) is the length substantially corresponding to distance (D1) between cutting position (P1) of the cutting mechanism and nipping position (P2) of a pair of first conveying rollers and that when rearmost end divided region (Sr1) passes through the nipping position of the pair of first conveying rollers, the pair of first conveying rollers are rotated 90° or more.