PURPOSE: To prevent cipher number from mischievous alterations by providing a cipher number setting button on the side of a panel for operating a cipher number key to unlock an electric lock and disabling the operation of the setting button in closing a door.

CONSTITUTION: When cipher number is inputted from an operating panel 55 while a gate door 1 is closed, an electric lock is unlocked to open the door. A cipher number setting button 50 is provided on the side of the operating panel 55. When the cipher number is set or altered, the door is opened after the lock is once unlocked by the prior cipher number. The setting button 50 is depressed from an opening hole 11 provided in the gate door 1 to set or alter the cipher number according to a predetermined operation. The cipher number can be prohibited from being set or altered while the gate door is closed. Thus, the mischievous alterations of the cipher number can be prevented.