A three-dimensional image optical system including at least an elementary image optical subsystem constructed with plural afocal optical elements which include the first and the second optical components, wherein the plural afocal optical elements are aligned in a planar arrangement. The variety of the focal length to satisfy the afocal property is realized with the combination of the first optical components and the second optical components, that results in to provide the flexibility of the depth magnification, by which a remote observation is possible.