Abstract: A room lamp fixing structure having a temporary fixing means provided for a room lamp and a ceiling trim and a permanent fixing means provided for the room lamp and a ceiling framework of a car body. This construction includes a ceiling trim having a recess for accommodating the room lamp, the recess having its side surface inclined so as to become gradually narrow from the opening portion to the bottom portion, and a room lamp having in its side surface a guide projection for positioning the room lamp and the ceiling trim by abutting against the slant side surface of the recess during the permanent fixing. This structure allows the guide projection to abut against the slant side surface, and thereby the room lamp and the ceiling trim are positioned.