PURPOSE: To provide a moderation applying mechanism which can install an arm rest, obviating the necessity of the special working and tools, and with which a strong elasticity can be obtained, and the generation of abnormal noise can be suppressed.

CONSTITUTION: A shoulder laying seat 3 is equipped with a rotary horizontal shaft 15, and the left and right walls 19 of a modertation applying member 18 are fitted into the groove of a U-shaped metal fitting 8 nearly free of gap, between the U-shaped metal fitting 8 of an arm rest 4. On the moderation applying member 18, a bulged-out part 23 which elastically contacts the top edge surface A of a rotary horizontal shaft 15 when the anm rest 4 is set to a used state and is once recessed by being pressed and then bulges-out again and elastically contacts the side surface C of the rotary horizontal shaft 15 when the arm rest 4 is turned to an accommodation state is formed. Further, on the outside of the installation hole 21 on the left and right walls 19 of the moderation applying member 18, an engagement cylinder part 22 engaged with an insertion hole 14 is installed.