An image processing device comprising: a shape estimation unit configured to estimate a three-dimensional shape of a subject by applying a shape-from-shading technology to an image of the subject; a storage unit configured to store the three-dimensional shape of the subject; and a correction unit configured to generate a quadratic surface connecting a plurality of points on the subject on the basis of the three-dimensional shape of the subject, to develop, on the basis of the quadratic surface, each of the plurality of points to a first planar surface that is tangent to the quadratic surface at a tangent point (Pc), to set each point (Q') on a corrected image as a process-target point, to obtain a first point on the first planar surface corresponding to the process-target point, to obtain a second point on the quadratic surface corresponding to the first point by using a first condition, a second condition and a third condition, to obtain a third point on the image of the subject corresponding to the second point, to calculate a pixel value corresponding to the third point by an interpolation process using a plurality of pixel values of the image of the subject, and to set the pixel value corresponding to the third point as a pixel value of the process-target point, wherein the first condition is that the second point is on the quadratic surface, the second condition is that a distance from the tangent point (Pc) on the quadratic surface to the second point is identical to a distance from the tangent point (Pc) to the first point on the first planar surface, the third condition is that the second point is on a second planar surface that cuts the first planar surface and the quadratic surface, and the second planar surface passes through the tangent point (Pc) and the first point and is perpendicular to the first planar surface, and wherein a normal vector of the second planar surface is obtained from an outer product of a normal vector of the first planar surface and a vector from the tangent point (Pc) toward the first point, and the third condition is expressed by using the normal vector of the second planar surface. a shape estimation unit configured to estimate a three-dimensional shape of a subject by applying a shape-from-shading technology to an image of the subject; a storage unit configured to store the three-dimensional shape of the subject; and a correction unit configured to generate a quadratic surface connecting a plurality of points on the subject on the basis of the three-dimensional shape of the subject, to develop, on the basis of the quadratic surface, each of the plurality of points to a first planar surface that is tangent to the quadratic surface at a tangent point (Pc), to set each point (Q') on a corrected image as a process-target point, to obtain a first point on the first planar surface corresponding to the process-target point, to obtain a second point on the quadratic surface corresponding to the first point by using a first condition, a second condition and a third condition, to obtain a third point on the image of the subject corresponding to the second point, to calculate a pixel value corresponding to the third point by an interpolation process using a plurality of pixel values of the image of the subject, and to set the pixel value corresponding to the third point as a pixel value of the process-target point, wherein the first condition is that the second point is on the quadratic surface, the second condition is that a distance from the tangent point (Pc) on the quadratic surface to the second point is identical to a distance from the tangent point (Pc) to the first point on the first planar surface, the third condition is that the second point is on a second planar surface that cuts the first planar surface and the quadratic surface, and the second planar surface passes through the tangent point (Pc) and the first point and is perpendicular to the first planar surface, and wherein a normal vector of the second planar surface is obtained from an outer product of a normal vector of the first planar surface and a vector from the tangent point (Pc) toward the first point, and the third condition is expressed by using the normal vector of the second planar surface.