1. An image processing device comprising: a comparison portion that compares a first image and a second image; and a determination portion that determines, based on a comparison result of the comparison portion, which of the first image and the second image is the image for a right and which is the image for a left, wherein the comparison portion extracts a block of a predetermined size at a predetermined position of the first image, performs template matching of the extracted block on the second image, and compares a position of a matching block on the second image with the position of the block of the predetermined size on the first image.