PURPOSE: To provide the title armrest capable of being comfortably used by the sitting persons on respective left and right seats even when the positions of a pair of the left and right seats are shifted before and behind by the physique difference between the sitting persons.

CONSTITUTION: The outside part of the armrest attached to one side part of a seat for a vehicle so as to be revolvable in a before-and-behind direction is constituted so as to be movable in the before-and-behind direction with respect to the inside part of the armrest and can be positioned and fixed at an arbitrary position by combining leaf springs 41 and corrugations 50c.