The invention provides a center lock device for automobile wheels wherein a center shaft portion integrally projects forwardly from the conical barrel of an adapter in the form of a top type or cylinder hat type, and a center nut is threadedly engaged with a male thread cut in the center shaft portion whereby a wheel disk is removably exchangeably fixed to the hub of an axle. The center lock device being characterized in that in order to attain durability strength, safety and steal prevention in the wheel attached state, the center shaft portion is centrally formed with a female thread for receiving a keep bolt such that the spiral pitch and spiral direction of the female thread differ from those of the female thread, and a keep bolt having a head larger in diameter than the center shaft portion is threadedly engaged with the female thread from the front, so that the center nut is locked against loosening by the large-diametered head of the keep bolt.