Abstract: An impact absorbing plate 31 is disposed between a front part 31z of the impact absorbing plate 31 and a vehicle body 11 so that a rupture generating part 44 ruptured by impact is extended in the front and rear direction of the vehicle, and the impact absorbing plate 31 is fixed to a front part 13a and a rear part 13b of the front seat bracket 13 provided in the vehicle body by rivets 33 and 33. A portion of front part 31z of the impact absorbing plate 31 is cut to form a cutoff part 45, and a front end 17a of a rail 17 provided in a seat section is attached to a convex part 35, which is molded so as to expand upward an inner side of the cutoff part 45, by a rivet 34.