PURPOSE: To easily release a locking button by a release bar of a luggage carrier by providing a link device between a working device and a pipe so as to transmit unlocking force to the locking device from the working device.

CONSTITUTION: A plunger 28 is positioned between link rods 30, 31. This plunger 28 has a truncated conical cam surface 48 to be engaged with an inclined cam surface 49 of the link rod 30 and an inclined cam surface 50 of the link rod 31. Downward pressurization of the plunger 28 by sufficient and large force to overcome springing force of a spring 45 drives the link rods 30, 31 outside of the plunger 28 until the link rods 30, 31 are engaged with locking buttons 21, 23 of pipes 13, 15 and presses the locking buttons 21, 23 to the inside of the pipes 14, 16. Consequently, the link rods 30, 31 can slide between the pipes 14, 16 of pipe assemblys 11, 12 by releasing the locking buttons 21, 23.