Near a discharge device (48) for discharging paper (P) with an image formed thereon, there is provided a punch (7) for punching holes. The drive of the discharge device (48) is controlled so that the punch punches the punch holes in the trailing portion of the paper (P), without causing creasing or tearing or change in the quality of the paper (P). The punch (7) includes punching cutters (72) and a punching die (74). The punching cutters (72) and the punching die (74) are provided in a unit (U) which can be drawn out of a casing (1) covering the punch (7). With the unit (U) drawn out of the casing (1), jam recovery can be easily executed. The unit (U) is movable in the width direction of the paper (P), thereby making it possible to adjust the position of punched holes. A collecting box (76) for collecting paper scraps (P1) is disposed in the unit (U). If the collecting box (76) is pivoted or the opening (76a) thereof is lifted up when the unit (U) is pivoted, the paper scraps (P1) therein will not fall out. Delaying timing for plural punching cutters (72) to punch holes can reduce the load on the drive system.