1. An image processing method for processing an image generated by image pickup using an optical system, comprising: a step of acquiring the image; and a step of performing image restoration processing on the image using an image restoration filter created such that its filter values have a two-dimensional distribution based on aberration information of the optical system, wherein the image restoration filter is created by performing inverse Fourier transformation on a function created based on an inverse function of an optical transfer function of the optical system, and wherein the image restoration filter is a filter in which a position of a cell having a maximum absolute value among the filter values is shifted with respect to a position of a center cell of the image restoration filter by a shift amount according to at least one of an amount of distortion aberration of the optical system and an amount of chromatic aberration of magnification of the optical system, and which reduces a blur component of the image and at least one of a component of distortion aberration and a component of chromatic aberration of magnification of the image.