The image processing apparatus performs an image process on a first image produced by image capturing. The apparatus includes: a memory storing coefficient data containing coefficients to be used in an approximation function to approximate a PSF of an image capturing optical system, and a processor performs the image process. The processor produces an approximated point spread function by using the coefficient of the coefficient data corresponding to an optical state of the optical system in the image capturing and two of a pixel pitch of an image sensor, a kernel size of a filter to be used for a sharpening process on the first image and number of taps of the filter; produce the filter by using the approximated PSF; and produce a second image that is a sharpened image by applying the filter to the first image.