Abstract: A retractor device for a seat-belt that is provided at a joining portion between a side sill and a center pillar in a motorcar. In the side sill, a side sill outer and a side sill inner are welded together at least along their upper portions to form a closed loop cross-section. This side sill is provided with a stiffener and a retractor device is mounted to the stiffener. The stiffener comprises a base portion extending along a side wall portion and a bottom portion of the side sill inner and provided with an aperture for inserting and mounting the retractor device therethrough, a side sill cross-section reinforcement portion connecting the side wall portion with the bottom portion, and an extension portion extending upwards from the gap between the side sill outer and the side sill inner in the top welded portion of said side sill and welded with the center pillar.