1. An image display apparatus comprising: a display unit having a first display region configured to display a plurality of main image data one at a time and a second display region located within the first display region and configured to display sub image data, the second display region including at least a first sub display region and a second sub display region, positions of the first sub display region and the second sub display region relative to the first display region being set in advance; a face region detecting section configured to detect a face region in the main image data; a face importance degree determining section configured to determine a face region importance degree of the face region detected by the face region detecting section; a calculating controller configured to calculate a first sub image display region importance degree of the first sub display region and a second sub image display region importance degree of the second sub display region based on the face region importance degree of the face region; and a display position setting section configured to set one of the first sub display region and the second sub display region as a display position where the sub image data is displayed based on the first and second sub image display region importance degrees.