An optical filter (50, 60, 70), comprising: a liquid crystal layer having first and second regions adjacent to each other which are capable of dividing incident light into at least two kinds of lights having different polarized states and emitting the divided lights, characterized in that the optical filter (50, 60, 70) further comprises a light transmission control region in the boundary between the first and second regions; the optical filter (50, 60, 70) controls a signal for a right eye and a signal for a left eye to have different polarized states from each other, wherein the signals for the right eye and for the left eye are emitted from a stereoscopic image display device comprising a display part comprising signal generating regions for a right eye and a left eye to generate the signals for the right eye and left eye; and a first light transmission control region adjacent to the signal generating regions for the right eye and the left eye; and the light transmission control region is formed so that the maximum value of its viewing angle "θ U " satisfying Expression 2 and the maximum value of its viewing angle "θ L " satisfying Expression 3 are three degrees or more: tan θ U = H 1 + 2 ⁢ y / 2 ⁢ T tan θ L = H 1 + 2 ⁢ H 2 - 2 ⁢ y / 2 ⁢ T where H 1 is the width of the first light transmission control region of the stereoscopic image display device, H 2 is the width of the light transmission control region of the optical filter (50, 60, 70), T is the distance from the display part to the optical filter (50, 60, 70) in the device to which the optical filter (50, 60, 70) is applied, and y is the distance from a spot at which an imaginary normal line of a line bisecting the width of the first light transmission control region of the device to which the optical filter (50, 60, 70) is applied with respect to a surface of the first light transmission control region is in contact with the light transmission control region to a part of the optical filter (50, 60, 70) in which the light transmission control region is present. a liquid crystal layer having first and second regions adjacent to each other which are capable of dividing incident light into at least two kinds of lights having different polarized states and emitting the divided lights, characterized in that the optical filter (50, 60, 70) further comprises a light transmission control region in the boundary between the first and second regions; the optical filter (50, 60, 70) controls a signal for a right eye and a signal for a left eye to have different polarized states from each other, wherein the signals for the right eye and for the left eye are emitted from a stereoscopic image display device comprising a display part comprising signal generating regions for a right eye and a left eye to generate the signals for the right eye and left eye; and a first light transmission control region adjacent to the signal generating regions for the right eye and the left eye; and the light transmission control region is formed so that the maximum value of its viewing angle "θ U " satisfying Expression 2 and the maximum value of its viewing angle "θ L " satisfying Expression 3 are three degrees or more: tan θ U = H 1 + 2 ⁢ y / 2 ⁢ T tan θ L = H 1 + 2 ⁢ H 2 - 2 ⁢ y / 2 ⁢ T where H 1 is the width of the first light transmission control region of the stereoscopic image display device, H 2 is the width of the light transmission control region of the optical filter (50, 60, 70), T is the distance from the display part to the optical filter (50, 60, 70) in the device to which the optical filter (50, 60, 70) is applied, and y is the distance from a spot at which an imaginary normal line of a line bisecting the width of the first light transmission control region of the device to which the optical filter (50, 60, 70) is applied with respect to a surface of the first light transmission control region is in contact with the light transmission control region to a part of the optical filter (50, 60, 70) in which the light transmission control region is present.