1. An image processing device comprising a pixel-interpolation processing unit that generates a sensitivity level value of an insufficient color component according to interpolation processing of image signals obtained by image pickup of a subject image, wherein the pixel-interpolation processing unit includes an arithmetic unit that outputs a sensitivity level value of the insufficient color component in the pixel of attention according to an arithmetic operation corresponding to an acquired color component, a sensitivity level value of which is acquired for the pixel of attention, and with an axis in a height direction perpendicular to two-dimensional directions, in which pixels are arrayed, set as an axis representing a sensitivity level value, assuming a first geometric figure that is a geometric figure including, as vertexes, the sensitivity level value acquired for the pixel of attention and sensitivity level values acquired for a plurality of first reference pixels that are pixels located near the pixel of attention and have acquired color components same as that of the pixel of attention, and a second geometric figure that is a geometric figure including, as vertexes, acquired sensitivity level values for a plurality of second reference pixels that have color components other than the acquired component of the pixel of attention as acquired color components and are located near the pixel of attention, the arithmetic unit calculates, such that the second geometric figure has a shape similar to that of the first geometric figure, a sensitivity level value of the insufficient color component in the pixel of attention and uses a same figure as the geometric figure irrespectively of which color component the acquired color component of the pixel of attention is.