An image display apparatus comprises a reference image display unit, a setting unit, an image generating unit and a tomographic image display unit. The reference image display unit displays a reference image on a display unit. The setting unit sets a display range of tomographic images in a first direction and either of a number of the tomographic images in the first direction to be displayed or a thickness of the tomographic images in the first direction, to image data corresponding to a plurality of slices. The image generating unit generates either of the tomographic images having the set thickness in the first direction or the set number of the tomographic images in the first direction using image data corresponding to a plurality of slices in the display range. The tomographic image display unit displays the generated tomographic images.