To surely protect a crew member in collision, etc. by smoothly making an arm-rest-upper leap with respect to an arm-rest-lower, and by surely breaking the arm-rest-lower by an impact load.

A rib 7 is vertically arranged on the inner surface of the arm-rest-upper 5 so as to project toward the upper surface 4a side of the arm-rest-lower 4. The abutting surfaces 8a, 8b between the rib 7 and the upper surface 4a of the arm-rest-lower 4 are formed to be tilting surfaces descending toward a door trim body 1 side respectively. As a result, when the arm-rest-upper leaps by making the abutting surface of the arm-rest-upper 5 slide with respect to the abutting surface of the arm-rest-lower 4, the arm-rest-upper leaps making the car room side as a fulcrum. As the door trim body 1 side of the arm-rest-upper 5 leaps, the arm-rest-upper 5 moves so as to separate from the door trim body 1. Thus, the leap of the arm-rest-upper 5 can be smoothly carried out.