Abstract: An apparatus and a method for fastening a screw between a vehicular lighting device body and lens is provided, in which there is no possibility that a seal material drips out. A lamp body is held by the lower jig so that a seal groove is directed upward, and a front lens is held by an upper jig so that a seal leg is directed downward. The upper jig is lowered from a position above the lamp body and pressed together therewith, so that the seal groove and the seal leg are engaged together via a seal material. A fastening screw is positioned beneath the lamp body (seal groove) with the fastening screw directed upward by a screw fastener element located within a lower portion of the lower jig. The lamp body (seal groove) and the front lens (seal leg) are pressed and secured by the screw. No seal material drips out from the seal groove in the process. Further, the time required for pressing together and fastening the lamp body to the front lens can be shortened.