There is provided a sensor 48 for detecting penetration of a sheet by a punch hole aligning pin 42, and there is provided controlling means for retrying a penetrating operation by returning the punch hole aligning pin to an initial position when a time period from starting to move the pin to penetrating the sheet exceeds a reference time period. Even when a degree of unalignment of the punch hole of the sheet P is considerable and the punch hole aligning pin cannot penetrate through the sheet by once, the punch hole aligning pin is penetrated therethrough frequently by repeating the penetrating operation and therefore, an error in aligning the sheet can be reduced. In a case in which the pin is not penetrated through the sheet even when the penetrating operation is carried out by a predetermined number of times, the pin is returned to the initial position and an error is displayed.