PURPOSE: To raise the safeness of unlocking by a method in which unlock command is converted to a supersonic wave in an unlocker and the unlock command is reconverted to send it to a device to be unlocked, having a locking and unlocking means, to release locking.

CONSTITUTION: An unlocking system consists of an unlocker 20 and a device 40 to be unlocked, The unlocker 20 is made up of an information former 1 and a supersonic wave converter 2 to convert the former 1 to supersonic wave. The device 40 is made up of a reconverter 18 to convert supersonic wave to unlocking signal and a lock releasing means 21 to unlock according to signals from the reconverter 18. Unlocking information from the unlocker 20 is converted to supersonic wave and sent to the device 40, and on the basis of the information, lock is released by the means 21. The safeness of unlocking can thus be secured.