A lighting device for a vehicle includes a mechanism for preliminarily fitting a lens to an extension before it is firmly fitted to a housing of the lighting device. To assure that a lens fitting operation is easily achieved at a reduced cost, a fitting hole is formed through an auxiliary foot portion extending from a housing fitting foot portion of the lens. A boss in the form of a tapered pin-shaped projection extends from the extension at the position corresponding to that of the fitting hole. In addition, a flange portion is formed at the upper end of the extension. The lens fitting operation is performed by inserting the boss into the fitting hole while the flange portion is placed on the upper surface of one of the side walls defining a lens receiving groove formed at the upper end of the housing of the lighting device. In the case that there is no possibility that water invades in the interior of a lighting chamber of the lighting device, the fitting hole may be formed directly through the housing fitting foot portion.