PURPOSE: To easily install a grommet for gas sealing.

CONSTITUTION: A grommet 12 in which a wire 11 is inserted to each wire insertion hole 15 is fixed in a sealed condition through a lock 13 of resin to an outer surface of an aperture 31 provided in a box 10 installed close to a battery for power supply in an electric car. The lock 13 is engaged on the outer side the grommet 12, a protrusion 21 for a support point protruded in the lock 13 is inserted into a support frame part 33 protruded in a box outer surface, and it is rotated about the protrusion 21 as the support point, so a locking protrusion 20 at a facing position is inserted into a locking frame part 32 protruded in the box outer surface for fixing the lock 13 to the box 10, where a seal rib 16 in the grommet 12 is pressed by the lock 13 to a circumferential edge of the aperture 31.