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 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 one of an amount of distortion 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 and a component of chromatic aberration of magnification of the image.