Abstract: A lock for an automatic vending machine including the combination of a bolt-and-nut locking mechanism and a slide locking mechanism. The bolt-and-nut locking mechanism includes a bolt movably mounted to the door of the vending machine to permit an associated handle to push and insert the bolt in a female-threaded hole of a nut on the casing body of the vending machine for locking at an intermediate level of the door of the vending machine. The slide locking mechanism includes a slide plate which is responsive to rotation of the bolt for sliding longitudinally until the slide plate has been caught by catching means on the casing body of the automatic vending machine, thereby locking the door to the casing body of the vending machine at upper and lower levels.