An image processing device includes a unit for reducing original image data of an image scanned by a scanning unit to generate a preview image; a unit for saving/reading a preview image data item of the preview image data in/from a memory; a unit for transferring the preview image data item saved in the memory to a display unit; a unit for inputting information indicating a relationship between a main scanning direction in which the image is scanned and an upper side of the image; and a unit for changing an arrangement order of pixels in the preview image data item such that the main scanning direction extends from a left side to a right side and the sub scanning direction extends from the upper side to a lower side of the preview image, as viewed with the upper side of the preview image at the top.