An optical element includes a three-dimensional structure having a curved surface; and a retardation plate bent along the curved surface. The retardation plate includes a transparent substrate and a liquid crystal layer formed over the transparent substrate. The retardation plate has a slow axis and a fast axis. A glass-transition temperature, Tgne, in a slow axis direction of the retardation plate is higher than a glass-transition temperature, Tgno, in a fast axis direction of the retardation plate.