1. An image processing device, including: a resolution conversion unit configured to convert a resolution of one viewpoint image out of a first viewpoint image imaged at a first resolution and a second viewpoint image imaged at a second resolution which is lower than the first resolution to the resolution of the other viewpoint image, and generate the first viewpoint image and the second viewpoint image both having a same resolution; and a generation unit configured to generate a disparity map based on a correlation value between the first viewpoint image and the second viewpoint image both having the same resolution and generated by the resolution conversion unit.