1. An eye tracking apparatus for detecting an eye in image data obtained in chronological order by picking up images of a face and tracking the detected eye, comprising: a threshold storing unit for storing a threshold; a tracking area storing unit for storing a tracking area; and a controller, capable of performing operations of: identifying a first area of an eye in image data; causing the tracking area storing unit to store the identified fist area as a tracking area; identifying a second area of an eye in image data subsequent to the image data on the basis of the tracking area stored in the tracking area storing unit; calculating a correlation value between the tracking area and the second area; and comparing the calculated correlation value with the threshold stored in the threshold storing unit, wherein the tracking area storing unit stores the second area identified by the controller as a tracking area when a comparison result by the computer indicates that the correlation value is larger than the threshold.