A sheet post-processing apparatus that performs a cutting process on a booklet formed by a bundle of center-folded sheets of paper includes: a conveying member that conveys the booklet; a leading edge stopper capable of reciprocating in a booklet conveying direction and used for setting a cutting position by abutting on a center-folded portion of the booklet; and a supporting member that supports the booklet when the cutting position of the booklet is to be set. When the booklet is being conveyed, the conveying member and the conveyed booklet are located in a contact position, and when the cutting position of the booklet is to be set, each of the conveying member and the conveyed booklet is located in one of separated positions, and the cutting position of the booklet is set by the leading edge stopper while the conveyed booklet is supported by the supporting member.