Provided is a technique of making auxiliary lines easy to view when displaying a stereoscopic image using radiological images. Auxiliary lines are added on two radiological images for displaying a stereoscopic image, respectively. The auxiliary lines are made up of a plurality of grids appearing to be arranged in the depth direction, and, on the auxiliary lines that constitute a grid on a rear side, intersections with the auxiliary lines that constitute a grid on a front side and the near portion of the intersections are removed. In this way, the intersections of the grids can be viewed easily.
