PURPOSE: To eliminate the defects of a lock for the conventional sliding doors by a method in which a clamp metal and a hooking lever are advanced from a lock body into a lock receiver, and a hook is operated to an engaging position with the clamp metal through a hooking drive lever toward the hooking lever for locking.

CONSTITUTION: When an unlocked sliding door is closed and locked, a clamp metal 3 is projected from a lock body 1 and advanced through the opening 23 of a side plate 22 into a lock receiver 19, as shown in the upper stage of the Fig. A hooking lever 4 goes into the lock receiver 19 and a hook 21 is turned to the engaging position with the crossing part 7 of the metal 3 and locked, as shown in the intermediate stage of Fig., while pressing the sloped portion 26 of a hook drive arm 25. In unlocking operation, the lever 4 goes into the lock body to release the couplement of the hook 21 and the metal 3, as shown in the upper stage of Fig., and the metal 3 retracts into the lock body for unlocking. When the lock is operated on the position where the sliding door is opened and then the door is closed, the hook 21 operated by the arm 25 slides on the side face of the metal 3 to complete locking state.