1. An image processing apparatus that generates a second image having a second resolution using a plurality of first images having a first resolution, the first images being captured using an image capture device, the image processing apparatus comprising: a first acquiring unit configured to acquire a relative movement amount between a reference image selected from the plurality of first images and each of the plurality of first images; a first generating unit configured to generate a fourth image having the first resolution for each of the plurality of first images in accordance with the relative movement amount corresponding to each of the plurality of first images, a third image having the second resolution, and image capture characteristics of the image capture device; a second acquiring unit configured to acquire an evaluation value based on a difference between each of the plurality of fourth images generated by the first generating unit and the first image corresponding to each of the plurality of fourth images; and a second generating unit configured to generate the second image having the second resolution by updating the third image using an update value that is determined using the plurality of fourth images in accordance with the plurality of evaluation values acquired by the second acquiring unit, wherein the second generating unit determines the update value using weights based on the plurality of evaluation values acquired by the second acquiring unit.