PURPOSE: To ensure robbery prevention by installing locking pieces having different lengths or oriented in different directions to locking bars which are actuated by a key and individually engaging the locking pieces to the receiving seat of each door so that a plurality of doors may not be opened simultaneously.

CONSTITUTION: In order to make the door 2 of the commodity selling or display section, the door 3 of a cash receiving section, the door 4 of machinery section, etc., of an automatic vending machine, etc., lockable and unlockable from a single lock 12, a plurality of locking pieces (bolts) 7 having different lengths and oriented in different directions is installed to locking bars 8, 9, 10, and 11. The operation of a key 5 is predetermined for unlocking the doors 2, 3, and 4 in such a way that, when, for example, the door 2 is unlocked, the key 5 is inserted into the lock 12 and turned by 3/4 round clockwise and, when the door 3 is unlocked, the key 5 is turned by 1/2 round counterclockwise and, further, supplementarily or additionally rotated, and so on. When persons in charge of replenishing commodities, collecting cash, servicing machines, etc., open the doors under their charge, the other doors are prevented from being opened. Therefore, robbery prevention can be ensured.