An object is designated as a designated object. Two or more image data items containing objects each being different from the designated object by an amount smaller than or equal to a first predetermined value are selected from among a specific image data item group. The selected two or more image data items are displayed in two or more display regions provided on a display unit. The objects each being different from the designated object by the amount smaller than or equal to the first predetermined value are defined as main objects, the two or more image data items are adjusted such that differences in position and size of the main objects in the display regions between the two or more image data items are made smaller than or equal to a second predetermined value, and the adjusted two or more image data items are displayed.