A polarization-variable element comprising a photochromic layer; and a guest host liquid crystal cell, wherein the guest host liquid crystal cell comprises a guest host liquid crystal layer which comprises liquid crystals and an anisotropic dye, a first electrode film and a second electrode film on both sides of the guest host liquid crystal layer, and a first alignment film and a second alignment film are formed on sides of the first electrode film and the second electrode film facing the guest host liquid crystal layer, respectively; wherein the polarization-variable element further comprises a substrate disposed on the opposite side of the photochromic layer facing the guest host liquid crystal layer, wherein the photochromic layer and the first electrode film are bonded via an adhesive, wherein the guest host liquid crystal layer is switchable between a horizontal orientation state and a vertical orientation state depending on a voltage application, wherein the first alignment film and the second alignment film are included on both sides of the guest host liquid crystal layer, and an angle formed between orientation axes of the first alignment film and the second alignment film is 10 degrees or less, wherein the anisotropic dye is a material capable of anisotropic absorption of light in at least a part or all of a wavelength range of 400 nm to 700 nm, wherein light axes of liquid crystal molecules in the horizontal orientation state are parallel to each other, wherein the photochromic layer satisfies Equation 1: A − B ≥ 50% wherein, A is a transmittance (%) of the photochromic layer before ultraviolet irradiation at ΔTmax wavelength, B is a transmittance (%) of the photochromic layer after ultraviolet irradiation at ΔTmax wavelength, and the ΔTmax wavelength means a wavelength having a largest difference in transmittance of the photochromic layer before and after ultraviolet irradiation, wherein ΔTmax wavelength is in the range of 500 nm to 600 nm. a photochromic layer; and a guest host liquid crystal cell, wherein the guest host liquid crystal cell comprises a guest host liquid crystal layer which comprises liquid crystals and an anisotropic dye, a first electrode film and a second electrode film on both sides of the guest host liquid crystal layer, and a first alignment film and a second alignment film are formed on sides of the first electrode film and the second electrode film facing the guest host liquid crystal layer, respectively; wherein the polarization-variable element further comprises a substrate disposed on the opposite side of the photochromic layer facing the guest host liquid crystal layer, wherein the photochromic layer and the first electrode film are bonded via an adhesive, wherein the guest host liquid crystal layer is switchable between a horizontal orientation state and a vertical orientation state depending on a voltage application, a guest host liquid crystal layer which comprises liquid crystals and an anisotropic dye, a first electrode film and a second electrode film on both sides of the guest host liquid crystal layer, and a first alignment film and a second alignment film are formed on sides of the first electrode film and the second electrode film facing the guest host liquid crystal layer, respectively; wherein the polarization-variable element further comprises a substrate disposed on the opposite side of the photochromic layer facing the guest host liquid crystal layer, wherein the photochromic layer and the first electrode film are bonded via an adhesive, wherein the guest host liquid crystal layer is switchable between a horizontal orientation state and a vertical orientation state depending on a voltage application, wherein the first alignment film and the second alignment film are included on both sides of the guest host liquid crystal layer, and an angle formed between orientation axes of the first alignment film and the second alignment film is 10 degrees or less, wherein the anisotropic dye is a material capable of anisotropic absorption of light in at least a part or all of a wavelength range of 400 nm to 700 nm, wherein light axes of liquid crystal molecules in the horizontal orientation state are parallel to each other, wherein the photochromic layer satisfies Equation 1: A − B ≥ 50% wherein, A is a transmittance (%) of the photochromic layer before ultraviolet irradiation at ΔTmax wavelength, B is a transmittance (%) of the photochromic layer after ultraviolet irradiation at ΔTmax wavelength, and the ΔTmax wavelength means a wavelength having a largest difference in transmittance of the photochromic layer before and after ultraviolet irradiation, wherein ΔTmax wavelength is in the range of 500 nm to 600 nm.