In an image forming device, images of originals up to an upper limit number of stapling are read (S1 to S5) and image data thereof are processed (S6 to S8). If a paper sensor has detected a subsequent original even when the number of pages of the read images reaches NS0 (S1, S2), a finisher discharges a bundle of printed papers without stapling. Consequently, the number of the printed papers included in the discharged bundle is made less than the upper limit number. In a case where the number of the printed papers sent to the finisher (S12, S13) is less than a set number NS1 (S15), the bundle is discharged without being stapled after the number of the printed papers reaches NS1 (S17).