PURPOSE: To permit cost cut and improve working efficiency by forming a cut groove on a sealing member and installing said sealing member by previously press-fitting the rib of said sealing member into the concaved groove of a lamp housing, when the periphery of the lamp on a chassis is sealed, thus obviating the necessity of wide seal due to counting on slippage.

CONSTITUTION: A seal member 10 has a cut groove 10a in the longitudinal direction, and when a lamp L2 is installed onto a chassis B2, said seal 10 is press- fitted into the concaved groove 11 on a stepped panel 9, previously putting the cut groove 10a into a rib 12. Then, the lamp L2 is inserted from a lamp housing 8 side into an installation port 6 on the chassis B2, and pushed onto a panel 7 on the port edge part, and a sealing member 10 is compressed, and then the lamp L2 is fixed onto the chassis B2 by means of fixing screws. Thus, ribbs 14 and 15 prevents slip of the seal member 10 press-fitted into the concaved groove 11, and the rib 12 prevents bending of the seal member 10 which is generated by compression.