Disclosed herein is a cross bar locking device of a roof carrier for a vehicle. The cross bar locking device includes a link, which is movably provided in the cross bar and has protrusion pins, and locking members, which are coupled to respective ends of the link so as to be axially movable. The locking member has a locking protrusion, to be locked to the corresponding locking hole of the associated side rail, and a plurality of protrusion pins. The cross bar locking device further includes levers, which are rotatably coupled to respective ends of the cross bar by a hinge. An operating slot is formed in each lever so that the protrusion pins of the corresponding locking member and the link are inserted into the operating slot. Movement guide slots are formed in the lever and communicate with the operating slot.