An optical beam deflection element including a phase panel controlling a polarization and a polarization grating plate causing birefringence based on the polarization, wherein the phase panel includes two substrates (41, 42; 61) having a corrugated sheet-like surface including recessed components and protruding components, and a polymer-stabilized blue phase liquid crystal inserted between the corrugated sheet-like surfaces of the two substrates disposed opposite to each other with a predetermined distance between the substrates, electrodes are formed into a corrugated sheet-like thin film on the corrugated sheet-like surface such that a positive voltage and a negative voltage can be applied to the electrodes formed into the thin films on the substrates by the blue phase liquid crystal, and the two substrates (41, 42) are disposed such that each of the protruding components of the corrugation of one of the substrates lies opposite to the recessed components that are included in the corrugation of the other of the substrates and that are adjacent to each other, or electrodes are formed into a corrugated sheet-like thin film on each protruding component of the corrugated sheet-like surface such that a positive voltage and a negative voltage can be applied to the electrodes of each of the substrates by the blue phase liquid crystal in a lateral direction, and the two substrates are disposed such that the electrodes of the protruding components of one of the substrates lie opposite to valley components each between the electrodes formed on the adjacent protruding components of the other of the substrates, the phase panel operates as a substantially isotropic medium in a case where no voltage is applied to the electrodes, and operates as a half-wave plate at a wavelength used in a case where a voltage is applied to the electrodes, each of the corrugated sheet-like thin films is formed of a material that is transparent at an optical wavelength used, the polymer-stabilized blue phase liquid crystal is stabilized by irradiation with light, the polarization grating plate includes a plurality of plate segments provided in a plane of the polarization grating plate and each plate segment consists of birefringent media with a thickness of a half-wave plate at the wavelength used, each of the plate segments is rectangular or circular and has a birefringence axis rotating with a predetermined period A that is not uniform within the plane of the polarization grating plate, and one or both of the period and a rotating direction of the birefringence axis varies among the plate segments, and the phase panel and the polarization grating plate is joined together in such a manner as to overlap. the phase panel includes two substrates (41, 42; 61) having a corrugated sheet-like surface including recessed components and protruding components, and a polymer-stabilized blue phase liquid crystal inserted between the corrugated sheet-like surfaces of the two substrates disposed opposite to each other with a predetermined distance between the substrates, electrodes are formed into a corrugated sheet-like thin film on the corrugated sheet-like surface such that a positive voltage and a negative voltage can be applied to the electrodes formed into the thin films on the substrates by the blue phase liquid crystal, and the two substrates (41, 42) are disposed such that each of the protruding components of the corrugation of one of the substrates lies opposite to the recessed components that are included in the corrugation of the other of the substrates and that are adjacent to each other, or electrodes are formed into a corrugated sheet-like thin film on each protruding component of the corrugated sheet-like surface such that a positive voltage and a negative voltage can be applied to the electrodes of each of the substrates by the blue phase liquid crystal in a lateral direction, and the two substrates are disposed such that the electrodes of the protruding components of one of the substrates lie opposite to valley components each between the electrodes formed on the adjacent protruding components of the other of the substrates, the phase panel operates as a substantially isotropic medium in a case where no voltage is applied to the electrodes, and operates as a half-wave plate at a wavelength used in a case where a voltage is applied to the electrodes, each of the corrugated sheet-like thin films is formed of a material that is transparent at an optical wavelength used, the polymer-stabilized blue phase liquid crystal is stabilized by irradiation with light, the polarization grating plate includes a plurality of plate segments provided in a plane of the polarization grating plate and each plate segment consists of birefringent media with a thickness of a half-wave plate at the wavelength used, each of the plate segments is rectangular or circular and has a birefringence axis rotating with a predetermined period A that is not uniform within the plane of the polarization grating plate, and one or both of the period and a rotating direction of the birefringence axis varies among the plate segments, and the phase panel and the polarization grating plate is joined together in such a manner as to overlap.