To achieve protection of a seated person more enough with a simple composition when waist and chest of the seated person is surely constrained respectively on a seat by front collision of the vehicle.

While providing to penetrate sliding holes 23 and 27 which slidably insert a midway part of a seat belt 18 longitudinally, and other sliding holes 24 and 28 into a shoulder anchor 25 and a tongue plate 29 respectively, a sliding hole 34 similar to the sliding holes 23, 24, 27 and 28 is provided to penetrate a lap outer anchor 19. One end part 18a side of a seat belt 18 that is an extension end side from a retractor 20 is made to be coupled with a lap outer anchor 19, after being made to be inserted to the sliding hole 23 of the shoulder anchor 25, the sliding hole 27 of the tongue plate 29, the sliding hole 34 of the lap outer anchor 19, the other sliding hole 24 of the shoulder anchor 25, and the other sliding hole 28 of the tongue plate 29 one by one.