PROBLEM TO BE SOLVED: To provide a preparation method of a retardation plate capable of conveniently preparing a retardation plate which has such a relation that the direction of making a refractive index of the retardation plate largest is perpendicular to the surface of the retardation plate and which is hardly achieved when using the conventional biaxial nematic phase, by providing a biaxial retardation plate of a new type using a biaxial liquid crystalline compound. SOLUTION: The retardation plate has an optically anisotropic layer formed by using at least one layer of liquid crystalline compound, wherein the liquid crystalline compound 1 exhibits biaxial smectic A phase (Fig.1 right). The preparation method of retardation plate comprises: a process of applying a composition which contains the liquid crystalline compound 1 exhibiting biaxial smectic A phase on a transparent support provided with an alignment layer as necessary to form a layer; a process of aligning the liquid crystalline compound 1 by forming the biaxial smectic A phase (Fig.1 right); and a process of making an optically anisotropic layer by fixing the aligned state. The liquid crystal display device uses the retardation plate. COPYRIGHT: (C)2008,JPO&INPIT