To prevent a lack of information which is desired to be displayed by switching of display forms.

The image display device includes: a display image extraction part 114 which extracts a display image to be displayed on a display 5 from a unit image; a display control part 14 which displays the extracted display image on the display 5; a specific image specification part 12 which specifies a portion of the display image displayed in a first display form; a display form-setting part 112 which changes the first display form into a second display form; an inclusion relation determination part 115 which determines whether or not an display image to be displayed in the second display form includes a portion of the display image displayed in the first display form; and an extraction range determination/changing means 113 for adjusting an extraction range of the display image to the unit image so that the display image to be displayed in the second display form includes a portion of the display image displayed in the first display form according to a determination result of the inclusion relation determination part 115, wherein the display control part 14 displays the display image extracted by the display image extraction part 114 within the adjusted extraction range on the display 5 in the second display form.

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