Disclosed herein is a cross bar of a roof carrier for vehicles, provided between side bars of a roof so as to load cargo, and having no wire, thus reducing a manufacturing cost. The cross bar includes first and second brackets provided on opposite ends of a cross-bar body. A first locking pin is provided on one end of the cross-bar body in such a way as to be retracted into and ejected from the first bracket. A second locking pin is connected to the other end of the cross-bar body via a power transmission unit, and moves in a direction opposite the moving direction of the cross-bar body to be retracted into and ejected out from the second bracket. A lever is provided on the first bracket. A body elastic part is provided between the cross-bar body and the second bracket, and provides restoring force to the cross-bar body.