Abstract: This antitheft device acts on the stand of the motorcycle to lock it in a lowered position. It comprises a lock unit attachable at two different positions to the frame of the motorcycle by means of a key, which is provided with a latch element. At one setting of the block, the latch element will not interfere with the movement of the stand, allowing normal use of the motorcycle, and at the other position, the latch element will inhibit the stand raising.