A screen image displaying image-data items in list form is displayed over a predetermined time period. Then, the display color of an image-data item of the image-data items, the image-data item corresponding to predetermined classification information, is changed so that the image-data item can be differentiated from other image-data items. Consequently, a user can clearly identify the classification of the image-data items and easily find an image-data item satisfying a condition without performing a complicated operation.