A light guiding plate is provided on the obverse side of a display for displaying a display image while varying the display image. Unevenness is formed at a predetermined position at a reverse surface of the light guiding plate. A light emitting element is disposed at the side surface of the light guiding plate in such a manner as to introduce the light to the light guiding plate. Alternatively, an uneven portion in conformity with a pattern of a desired display image may be formed at a reverse surface of the light guiding plate, and a light emitting element is disposed at the side surface of the light guiding plate in such a manner as to introduce the light to the light guiding plate.