PURPOSE: To display the position relation of the present display image on reconstitution images of one group by displaying a scale for showing the whole quantity of the reconstitution images and a cursor for showing the order of the images on a screen of a display device, and moving successively the cursor on the scale, whenever the display image is switched.

CONSTITUTION: When tomography image data is read out of a storage device 1, and its tomography image 15 is displayed on a screen of a display device, a scale 16 for showing the whole quantity of the tomography images of one group of a patient selected by a pointer 12 is displayed on a part of the same screen of the display device 5, based on tomography image information for constituting a slice directory 13, and also, a cursor 17 for showing the order of the tomography image 15 of the slice surface selected and displayed by the present pointer therein is displayed. In such a state, whenever the tomography image 15 displayed on the screen of the display device 5 is switched, the cursor 17 moves successively on the scale 16. In such a way, which exists the display order of the tomography image 15 presently being displayed among the tomography images of a certain group of patients can be known clearly at a glance.