To provide technique for reducing a tester's burden in performing detailed observation for a lesion part after the position of the lesion part is roughly specified by the conventional add image display.

This image diagnostic apparatus has a means for collecting reconfigured images obtained by slicing a measurement object, a means for adding plural reconfigured images collected by the above means, a means for generating a display image from the processed image after addition, and a means for displaying a display image on a display screen. The apparatus is provided with a means for setting the addition range of the reconfigured images, and a means for outputting the reconfigured images in the present range to the adding means, wherein the reconfigured images selected by the setting means are output to the adding means, and the adding means adds the reconfigured images in the output range and outputs the same to the display image generating means.