The sheet post-processing device includes a discharge port, a discharge tray, a first sheet holding member, and a second sheet holding member. The discharge port has a pair of discharge rollers that discharge a sheet including a folded sheet subjected to folding processing. The first sheet holding member and the second sheet holding member are, on a downstream side of the pair of discharge rollers in the discharge direction of the folded sheet, selectively disposed at a holding position, at which the first sheet holding member and the second sheet holding member intersect a discharge route for the folded sheet and extend downward from above the pair of discharge rollers toward the discharge tray to hold the folded sheet, and a retreat position retreated to above the discharge route for the folded sheet.