Abstract: An interpolation processing apparatus that performs interpolation to obtain color information corresponding to a first color component of a pixel, in which the first color component is missing, of an image-capturing sensor having a plurality of pixels which are arranged in a two-dimensional array and output color information corresponding to different color components, which are first-nth (n>2) color components, each of the plurality of pixels outputting color information corresponding to a single color component, includes: a similarity degree calculation unit that calculates each of similarity degrees along, at least, two directions relative to an interpolation target pixel to undergo interpolation processing by using a “different-color similarity component obtained by using color information corresponding to different color components” calculated with a “similarity degree element constituted of color information from three or fewer pixels”, based upon color information at a plural