PURPOSE: To prevent stapling at a position corresponding to a punch, in an image forming device having a function for automatically stapling a paper sheet on which an image is formed.

CONSTITUTION: The paper sheet ejected from an image forming device main body is matched and housed in a paper housing part 55, a head for stapling 70 is moved along one side of the housed paper sheet, to staple the sheet at its arbitrary position. The position of the stapling can be inputted from one a control panel. A constitution is adopted so that it is judged that the inputted position is one capable of obtaining the punch after this or not and when setting is attained at that kind of position, warning, etc., are issued to prevent the stapling at that kind of position.