The present invention intends to provide an optical element that can be incorporated in a liquid crystal display device, is provided with a birefringent layer obtained by aligning and polymerizing polymerizable liquid crystal molecules, and, while sufficiently reflecting an actual condition of a liquid crystal display device, can reduce fear that a thickness of a driving liquid crystal layer unexpectedly varies. An optical element includes a light-transmitting base material and a birefringent layer comprising of aligned and polymerized liquid crystal molecules and having a value of indentation depth of 6% or less relative to a thickness of the birefringent layer, wherein said value is measured under conditions where a cylindrical indenter having a diameter of 30 (.mu.m) is applied at a load of 10 mN/sec up to the maximum load of 400 mN.