Abstract: A locking device, particularly for a spare wheel cradle 12 mounted to pivot under the floor 14 of an automobile, the cradle being able to be released from inside the automobile by a control mechanism 28-34 connected to a locking mechanism 16 including a housing 18 mounted under the floor, a retaining hook 36 for retaining the cradle 12 and a safety hook 38, the cradle causing being automatically locked by the retaining hook when the cradle is put in place under the floor. The locking mechanism 16 includes a mechanism for retaining the safety hook in a retracted position when the cradle is in the released position, release of the retaining mechanism 100 being controlled by the automatic locking of the cradle 42 by the retaining hook 36.