The fit portions 10 of the right and left grommets 6 are structured such that each of the fit portions 10 extends across a portion of the wire harness covering cylindrical body 7 of the grommet 6 in the peripheral direction of the wire harness covering cylindrical body 7, the two side portions of such extending-across fit portion with the wire harness covering cylindrical body 7 as the boundary thereof are formed asymmetric in shape, and, when the right and left grommets 6 are positioned in the same direction, the fit portion 10 of the right grommet 6b is set so as to be rotated 180° with respect to the fit portion 10 of the left grommet 6a; in each of the right and left grommets 6, there is formed a display portion 12 which can be used to indicate the position and direction of the grommet 6 when assembling the same or can distinguish the assembling sides of the right and left grommets 6 from each other when assembling the same. On the other hand, the fit holes 8 of the right and left body panels 1, into which the fit portions 10 of the right and left grommets 6 are to be fitted, are disposed such that, on the right and left sides of the vehicle body, they are formed so as to be rotated 180° with respect to each other in correspondence to the setting of the fit portions 10 of the right and left grommets 6.