To eliminate tight feeling and difficulty of the use by adjusting a position of an arm rest along the width direction or the longitudinal direction not only along the vertical direction.

A guide part 5 is tilted with respect to the vertical direction, and guides movements of the arm rest 2 so that the arm rest 2 is separated to the vehicle width direction with respect to an occupant using the arm rest 2 along with upward movements of the arm rest 2.