An image processing apparatus includes a plurality of addition means and an image processing means. The addition means performs addition processing of adding pixels of a differential image at a second resolution representing a difference between an inputted image at a first resolution and an image at the second resolution higher than the first resolution as pixels of an inputted image at the second resolution. The image processing means is configured to perform second and subsequent addition processing, and generate an image of the second resolution as a processing result by performing the addition processing for a predetermined number of times. The addition processing is performed with inputs of an image at the first resolution and an image at the second resolution obtained by an immediately preceding addition processing, which are different from each other.