The invention relates to an indicating and/or lighting device for a motor vehicle, said device comprising a casing inside which there are arranged at least one main light source, at least one reflector associated with the main light source(s), optionally at least one intermediate screen that is substantially transparent and lies opposite said main light source or at least one of said main light sources, and a closing covering for the casing. At least one of the faces of the closing covering and/or of the optional intermediate screen is provided with a plurality of foci for diffusing light by means of surface alterations of said face.