1. A subject tracking apparatus for tracking a subject in images supplied in a time series manner, the subject tracking apparatus comprising: a reference image registering unit configured to register a reference image for use in tracking the subject; an extraction unit configured to extract, from a supplied image, a subject region which is similar to the reference image on the basis of a degree of correlation between the supplied image and the registered reference image; a position detection unit configured to detect the position of the subject in the subject region on the basis of a distribution of characteristic pixels representing the subject contained in the subject region; and a correction unit configured to correct the subject region so as to reduce a shift in the position of the subject in the subject region, wherein the corrected subject region is taken as a result of tracking the subject in the supplied image, and the reference image registering unit registers the corrected subject region as a reference image to be used for tracking the subject in a next supplied image.