Abstract: An image data processor, for use in a device which plays a battle game, a congeniality divination game, etc., includes a designating unit which is operated to designate respective parts of objects in order to display those object images on a display. A determining unit determines superiority or inferiority between the respective displayed object images on the basis of scores corresponding to part images constituting the respective displayed object images. The respective object images are changed depending on the results of the determination and the resulting object images are then displayed on the display. When the designating unit designates any part of the object, a score corresponding to that portion is read out, and data on the appropriate object image is displayed on the display depending on the read out score.