An image display device comprising: a projection port from which image display light is projected; and a combiner that presents a virtual image by reflecting the image display light generated based on an image signal projected from the projection port; wherein: with respect to a specific direction along a reflection surface of the combiner, the curvature of the combiner in the specific direction becomes smaller as a distance from the projection port becomes larger, the specific direction being a direction away from a vertex position at which the distance from the projection port is smallest; and the reflection surface of the combiner is formed by a shape that is asymmetrical using a biconic surface, wherein, when a visual-line direction in which the virtual image is visually recognized via the combiner is set to be a z-axis direction, a direction that is perpendicular to the z-axis direction, such that the visual-line direction and a projection direction are both contained in the yz-plane, is set to be an y-axis direction, and a direction that is perpendicular to the z-axis direction and the y-axis direction is set to be a x-axis direction, the combiner is provided at a position where a projection position at which the projection axis of the image display light projected from the projection port intersects with the reflection surface is different from a vertex position at which both the curvature in the x-axis direction and the curvature in the y-axis direction of the biconic surface forming the reflection surface become maximum, wherein the combiner is shaped into a form such that a line of intersection of the biconic surface forming the reflection surface and the x-z plane is an elliptic line and such that a line of intersection of the biconic surface forming the reflection surface and the y-z plane is a hyperbolic curve, wherein a conic constant ky in the y direction of the biconic surface forming the reflection surface satisfies a relationship of -1 > k y > -2. a projection port from which image display light is projected; and a combiner that presents a virtual image by reflecting the image display light generated based on an image signal projected from the projection port; wherein: with respect to a specific direction along a reflection surface of the combiner, the curvature of the combiner in the specific direction becomes smaller as a distance from the projection port becomes larger, the specific direction being a direction away from a vertex position at which the distance from the projection port is smallest; and the reflection surface of the combiner is formed by a shape that is asymmetrical using a biconic surface, wherein, when a visual-line direction in which the virtual image is visually recognized via the combiner is set to be a z-axis direction, a direction that is perpendicular to the z-axis direction, such that the visual-line direction and a projection direction are both contained in the yz-plane, is set to be an y-axis direction, and a direction that is perpendicular to the z-axis direction and the y-axis direction is set to be a x-axis direction, the combiner is provided at a position where a projection position at which the projection axis of the image display light projected from the projection port intersects with the reflection surface is different from a vertex position at which both the curvature in the x-axis direction and the curvature in the y-axis direction of the biconic surface forming the reflection surface become maximum, wherein the combiner is shaped into a form such that a line of intersection of the biconic surface forming the reflection surface and the x-z plane is an elliptic line and such that a line of intersection of the biconic surface forming the reflection surface and the y-z plane is a hyperbolic curve, wherein a conic constant ky in the y direction of the biconic surface forming the reflection surface satisfies a relationship of -1 > k y > -2. with respect to a specific direction along a reflection surface of the combiner, the curvature of the combiner in the specific direction becomes smaller as a distance from the projection port becomes larger, the specific direction being a direction away from a vertex position at which the distance from the projection port is smallest; and the reflection surface of the combiner is formed by a shape that is asymmetrical using a biconic surface, wherein, when a visual-line direction in which the virtual image is visually recognized via the combiner is set to be a z-axis direction, a direction that is perpendicular to the z-axis direction, such that the visual-line direction and a projection direction are both contained in the yz-plane, is set to be an y-axis direction, and a direction that is perpendicular to the z-axis direction and the y-axis direction is set to be a x-axis direction, the combiner is provided at a position where a projection position at which the projection axis of the image display light projected from the projection port intersects with the reflection surface is different from a vertex position at which both the curvature in the x-axis direction and the curvature in the y-axis direction of the biconic surface forming the reflection surface become maximum, wherein the combiner is shaped into a form such that a line of intersection of the biconic surface forming the reflection surface and the x-z plane is an elliptic line and such that a line of intersection of the biconic surface forming the reflection surface and the y-z plane is a hyperbolic curve, wherein a conic constant ky in the y direction of the biconic surface forming the reflection surface satisfies a relationship of -1 > k y > -2.