To provide a cipher operation opening and closing double lock for a door easily fitted to a lock provided on the existing door.

In this double lock, a first box frame having a first lock fixed to the door and physically strong, a fixing member mounted between the first lock and the door, and a solenoid for cipher operation opening and closing second lock for preventing picking, a second frame fixed between the fixing member and the first box frame by screw-fastening the fixing member and the first box frame by a long bolt, and a cover having a core insert hole for fitting a solenoid core formed in the lower side of the back are integrally constructed, whereby the solenoid is operated by cipher operation of the second lock to open and close the cover. Thus, the double lock can be fixed to the door of a building without a machining tool.