1. A subject tracking apparatus comprising: a region extraction section extracting a region similar to a reference image in a first image based on respective feature amounts of the first image being picked up and the reference image being set; a motion vector calculating section calculating a motion vector in each of a plurality of regions in the first image using a second image and the first image, the second image being picked up at a different time from that of the first image; and a control section determining an object region of subject tracking in the first image based on an extraction result in the region extraction section and a calculation result in the motion vector calculating section.