The image processing apparatus is provided with a preview image generating portion for generating a preview image of image data to be output in the unit of an output job, and an image display portion such as a touch panel for displaying the generated preview image. The image display portion displays a generation stop key for stopping generation of the preview image during the generation of the preview image so as to be selectable by a user, and displays a different screen in accordance with a generation state of the preview image when the generation stop key is selected by a user operation.