center on a rear end part of the recessed portion 5 a cutout 7 opened to the front is located somewhat to the front of the insertion hole 6 each recessed portion 5 includes a raised piece 8 vertically extending thereon the raised piece 8 has a front face 8a gently tapered down to the front and a rear face 8b directed rearward serving as an engaging face above and below each recessed portion 5 inward projecting portions 9 are formed at the locations on the outer side of the lamp body where are closer to the front end of the lamp body 2 the front face of each of the inward projecting portions 9 serves as a seat 9a directed to the front the seats 9a are flush with one another a mount base 10 is fixed to a portion on the lower surface of the lamp body 2 where is located closer to the rear end the mount base 10 formed of metal plate is hemispherical in shape the mount base 10 has a relatively larger insertion hole 10a a hemispherical attach plate 11 is formed of a metal plate a curvature of the attach plate 11 is equal to that of the inner surface of the mount base 10 an insertion hole 11a is formed at the central part of the attach plate 11 the attach plate 11 is placed on the inner surface of the mount base 10 a bracket 12 is fixed to a vehicle body 13 the bracket 12 has a substantially part spherical concavity 12a at the top thereof and further includes an insertion hole 12b a set bolt 14 is inserted into the insertion hole 11a of the attach plate 11 the insertion hole 10a.