A light modulation device comprising: a first polymer film substrate and a second polymer film substrate disposed opposite to each other and a light modulation film layer having a light modulation layer between the first polymer film substrate and the second polymer film substrate, wherein each of the first polymer film substrate and the second polymer film substrate has an in-plane retardation of 4,000 nm or more for light having a wavelength of 550 nm, wherein each of the first polymer film substrate and the second polymer film substrate is a stretched polymer film, wherein a respective first direction of each of the first polymer film substrate and the second polymer film substrate is an in-plane transverse direction and a respective second direction of each of the first polymer film substrate and the second polymer film substrate is an in-plane machine direction, characterized in that the in-plane transverse direction is a respective slow axis direction, and the in-plane machine direction is a respective fast axis direction, wherein each of the first polymer film substrate and the second polymer film substrate has a ratio (E1/E2) of an elongation in the first direction to an elongation in the second direction perpendicular to the first direction of 3 or more, wherein the first polymer film substrate and the second polymer film substrate are disposed so that an angle formed by the first direction of the first polymer film substrate and the first direction of the second polymer film substrate is in a range of o degrees to 10 degrees, wherein the elongation is measured by conducting a tensile strength test by applying a force at a tensile speed of 10 mm/min at room temperature (25 °C) and a specimen for measuring the elongation has a width of 10 mm and a length of 30 mm. a first polymer film substrate and a second polymer film substrate disposed opposite to each other and a light modulation film layer having a light modulation layer between the first polymer film substrate and the second polymer film substrate, wherein each of the first polymer film substrate and the second polymer film substrate has an in-plane retardation of 4,000 nm or more for light having a wavelength of 550 nm, wherein each of the first polymer film substrate and the second polymer film substrate is a stretched polymer film, wherein a respective first direction of each of the first polymer film substrate and the second polymer film substrate is an in-plane transverse direction and a respective second direction of each of the first polymer film substrate and the second polymer film substrate is an in-plane machine direction, characterized in that the in-plane transverse direction is a respective slow axis direction, and the in-plane machine direction is a respective fast axis direction, wherein each of the first polymer film substrate and the second polymer film substrate has a ratio (E1/E2) of an elongation in the first direction to an elongation in the second direction perpendicular to the first direction of 3 or more, wherein the first polymer film substrate and the second polymer film substrate are disposed so that an angle formed by the first direction of the first polymer film substrate and the first direction of the second polymer film substrate is in a range of o degrees to 10 degrees, wherein the elongation is measured by conducting a tensile strength test by applying a force at a tensile speed of 10 mm/min at room temperature (25 °C) and a specimen for measuring the elongation has a width of 10 mm and a length of 30 mm.