A reduced image generation portion generates a reduced image indicating the content of a file stored in a storage device. When a judgment portion judges that text data, which is the file in text format, is attached to the file, a display image generation portion generates a display image indicating the attachment of the text data to the file. A display control portion then displays the images generated by the reduced image generation portion and the display image generation portion on a display as one thumbnail image. Meanwhile, when the text data is not attached to the file, the display control portion displays the reduced image generated by the reduced image generation portion as the thumbnail image.