A sheet processing apparatus comprises: a conveying portion which contacts a doubled up booklet and conveys the booklet; an end conveying portion which abuts against an open end of the booklet and pushes out the booklet, thereby conveying the booklet; a stopper which abuts against a back of the booklet to position the booklet; a holding portion which holds the booklet which abuts against the stopper; a processing portion which processes the booklet held by the holding portion; wherein the conveying portion can come into contact with and separate from the booklet, the conveying portion separates from the booklet, or a pressure for bringing the conveying portion into contact with the booklet is reduced before the back of the booklet abuts against the stopper, the back of the booklet is abutted against the stopper by the end conveying portion and then, the holding portion holds the booklet.