PURPOSE: To promote safety by providing a double lock mechanism of master and slave locks to a safe-deposit-box, at the same time, providing a bio ID device detecting a physical characteristic of a user to the master lock, and unlocking the double lock mechanism in the case it corresponds with data registered in advance.

CONSTITUTION: A bio ID device 7 detecting a physical characteristic (for example, finger prints) of a user is provided to a gate 1 of a safe-deposit-box room 2, it is referred to data registered in advance, and in the case it corresponds therewith, the safe-deposit-box is unlocked. After that, a user entered in the safe deposit box unlocks the safe-deposit-box 3 by operating a slave lock consisting of a ten-key and a rotary dial, etc. It can be unlocked even if there is no key and, at the same time, the person oneself only can unlock the safe- deposit-box. According to the constitution, safety and reliability can be promoted.