1. An image processor that performs motion search by referring to a first image stored in an external memory, the image processor including: a first internal memory accessible with a higher speed than the external memory and configured to hold a second image in a predetermined range of the first image; an image production unit configured to read an image in a predetermined range of the second image from the first internal memory and produce a third image for rough search based on the read image; a second internal memory accessible with a higher speed than the external memory and configured to hold the third image produced by the image production unit; a first search unit configured to read the third image from the second internal memory and perform first motion search based on the third image; and a second search unit configured to read a fourth image in a predetermined range of the second image from the first internal memory based on a search result by the first search unit and perform second motion search that is more detailed than the first motion search based on the fourth image.