A sheet processing apparatus includes a conveyance member to convey a sheet, a pair of alignment members to move relatively in a width direction orthogonal to a conveyance direction of the sheet by the conveyance member, so as to align a position of the sheet in the width direction, and a lower portion to support a lower surface of the sheet between the pair of alignment members in the width direction. In addition, a pair of upper portions are arranged on one side and the other side of the lower portion in the width direction and each hold an upper surface of the sheet, wherein the pair of upper portions is positioned lower than the lower portion in a plane vertical to the conveyance direction.