PURPOSE: To prevent such trouble as breakdown of a utensil on a seat, an injury of an infant, etc., and to give a high class sense to the seat by attaching the device to the seat and the side face of a back rest of an automobile, and decelerating gradually a reclining speed, at the time of reclining the back rest of the automobile.

CONSTITUTION: This device is constituted of a seat bracket 1, a friction plate 2, a contact plate 3, a disc spring 4, a back rest bracket 5, a bolt 6, etc., and when a back rest S is reclined, the back rest bracket 5 is reclined toward the seat bracket 1, the bolt 6 whose head part is fixed to the back rest bracket 5 is screwed into a nut fixed to the seat bracket 1 and the disc spring 4 is compressed. Also, since the back rest bracket 5 and the contact plate 3 are rotated integrally, frictional force between the contact plate 3 and the friction plate 2 increases, and a reclining speed of the back rest S is decreased gradually.