Fold plate [C] center folds the stack lifted to the fold position by the bottom fence with the pressure of the fold transport motor [D]. Next, the side-to-side fold roller unit [E] forms the saddle shape. The press fold motor drives both the fold plate [C] and the side-to-side fold roller [E]. This is so that the fold plate [C] and side-to-side fold roller [E] can operate at the same time. [A] is the side-to-side fold unit HP sensor and [B] is the fold plate HP sensor.