1. An image processing apparatus, for processing original image data representing a captured color image that has been subjected to photoelectric conversion, comprising: estimation unit which generates estimated color fringing information representing an estimate of color fringing in the captured image on the basis of the original image data; removing unit which employs the estimated color fringing information to generate modified image data based on the original image data so as to compensate for such color fringing in at least a part of the captured image; a spatial calculation unit which uses, as a reference plane, a color plane other than a color plane from which said removing unit removes color fringing, and calculates a gradient of a signal intensity of a color plane; and a region determination unit which determines whether the color plane from which said removing unit removes color fringing is saturated, wherein said estimation unit selects either of a gradient of a signal intensity of the color plane subjected to removal and a gradient of a signal intensity of the reference plane on the basis of a determination result of said region determination unit and estimates the degree of color fringing in each region of the color image by using the selected gradient.