PURPOSE: To enable the magnification switching action of a displayed image at a high speed by providing a minified image memory unit and an image memory unit in series, and loading data reduced by half the original volume in the minified image memory at the same time as data is loaded into the image memory unit.

CONSTITUTION: First data such as the characters and symbols of a dial face 3 loaded through a photography section 19, is stored in a digitized memory unit 21 as a temporary data storage through a serial/parallel conversion section 20. Next, this stored data writes data in buffer memory 26 or blank print memory 30 in accordance with given purposes, if the former receives a command from a display control section 25. In addition, data such as guide-lines which are required for printing plate setting but are not yet used for printing are loaded in an image memory unit 27 by the display control section 25 based on an instruction given by the data entered from an input section 23 into a control section 22. In this case, the content of the mentioned data is loaded in a minified image memory unit 101 upon an instruction given by the display control section 25 after the reduction of said content to half its original volume.