An image forming device and method in which, when double-sided printing is carried out, placing an image of a first side and an image of a second side at a position determined in accordance with the position of the image of the first side; if it is judged a predetermined interval or more is needed between the respective placed images and images which have already been placed and are adjacent to the placed images, and judged that the predetermined interval or more is not maintained between them, placing again the images of the first and second sides at positions where the predetermined interval is maintained, are performed, is provided.