According to one embodiment, a liquid crystal optical element includes an optical waveguide including a first main surface and a second main surface opposed to the first main surface, an alignment film disposed on the second main surface, a liquid crystal layer which overlaps the alignment film, which includes cholesteric liquid crystals, and which reflects at least part of light incident through the optical waveguide toward the optical waveguide, and a transparent first protective layer which overlaps the liquid crystal layer, and which is formed of a water-soluble polymer or a fluorine-based resin.