An image processing apparatus has a function of printing pieces of image data to be printed arranging them on one printing paper sheet. In a preview display screen of the image processing apparatus, when a specific piece of image data is selected by a user's operation from a plural piece of image data, the specific piece of image data is displayed being distinguished. Pieces of image data in the same shooting orientation as that of the specific piece of image data are searched for and their display is similarly varied. At this time, when rotation of the images is selected using a dialogue, the orientation of the pieces of image data is rotated at once by 180°. Thereby, the orientations of pieces of image data shot in a portrait-like posture may easily be adjusted to be the same and their images may be printed according to the preview display.