A finisher includes an intermediate tray that collects sheets to form a sheet bundle, a sheet gripping member that grips one end of the sheet bundle in a conveying direction and a positioning member that grips the other end of the sheet bundle in a conveying direction, a moving portion that moves the sheet gripping member and the positioning member to come close to each other, a pair of folding rollers that folds the sheet bundle while conveying the sheet bundle, a projecting member that projects a part between the one end and the other end of the gripped sheet bundle toward the pair of folding rollers, and a controller that controls the moving portion, such that the sheet gripping member and the positioning member come close to each other in synchronization with an operation of projecting the projecting member toward the sheet bundle.