To improve an occupant's convenience by adding an additional function to an arm rest function for the occupant of a front seat.

An arm rest 10 positioned between left and right front seats 11 preferably has an arm rest face with cushion performance and a tray face at the opposite side facing it, and is rotatably mounted in a front and rear direction of a vehicle through a horizontal shaft 12 extending in a width direction of the vehicle relative to a bracket 11 of a rear end of a center console 3. The arm rest 10 has a two-split structure of a base end 14 coupled with the horizontal shaft 12 and an arm rest main body 15. The arm rest main body 15 is rotatably mounted through a shaft 16 relative to the base end 14. The arm rest face or the tray face is used by selectively and reversely turning the arm rest 10 around the shaft 16.