An image generation apparatus includes a plurality of irradiators, and a control circuit. The control circuit performs an operation including generating an in-focus image of an object in each of a plurality of predetermined focal planes, extracting a contour of at least one or more cross sections of the object represented in the plurality of in-focus images, generating at least one or more circumferences based on the contour of the at least one or more cross sections, generating a sphere image in the form of a three-dimensional image of at least one or more spheres, each sphere having one of the circumferences, generating a synthetic image by processing the sphere image such that a cross section appears, and displaying the resultant synthetic image on a display.