To provide an image forming device capable of preventing a printing error by performing warning display when printing is impossible.

This image forming device performing the copying operation of an original or the printing operation of an image is provided with an image area detection means for detecting an image area by reading the original or detecting the image area from inputted printing data, a printing area setting means for setting a printing area for outputted paper, a detection means (area decision part) 48 for detecting the presence/absence of the image area on the outside of the printing area, and a warning display means for performing the warning display that the printing is impossible when the image area is detected on the outside of the printing area. At the time of copying or printing, whether or not the image data exists on the outside of the printing area is judged according to the image area and the printing area of the outputted paper. In the case of detecting it, the warning display that printing is impossible is performed, whereby the printing error is prevented.