A double-sided printing apparatus for printing on both surfaces of a recording medium comprises a first image-forming unit 3 for forming the toner image on one surface of the recording medium, a second image-forming unit 4, provided downstream of the first image-forming unit 3, for forming a toner image on the other surface of the recording medium, a first flash fixing unit 50 for fixing the toner image on the first surface of the recording medium and a second flash fixing unit 51, provided downstream of the first fixing unit, for fixing the toner image on the other surface of the recording medium. An intermediate member 71 is provided between the first fixing unit and the second image-forming unit. This intermediate member may be a shielding member for preventing the light from the first fixing unit from reaching a photo-sensitive body of the second image-forming unit 4, and/or a guide member for guiding the recording medium; in the latter case a charger 40 for charging the recording medium P to prevent offset of the as yet unfixed image onto the guide member may also be provided.