A sheet processing apparatus including a stacking portion for stacking sheets, an alignment reference wall disposed in approximately parallel with a conveying direction of the sheet, an alignment moving wall for performing alignment by making an end portion of the sheet hit with the alignment reference wall, a processing mechanical section for carrying out binding with respect to the sheet bundle thus aligned, and a plurality of rotating pairs disposed in a widthwise direction approximately perpendicular to the conveying direction of the sheet for conveying the sheet bundle in a pinching manner. The sheet processing apparatus is capable of performing a process such as binding in the processing mechanical section after the sheet bundle which has been aligned by the alignment reference wall and the alignment moving wall is conveyed by a predetermined distance by the rotating pairs, and it is characterized in that each of the plurality of the rotating pairs disposed in the sheet widthwise direction has a pressure different from that of other rotating pairs for pinching the sheet.