To automatically operate an alarm when an unlocking operation is performed from the outside.

This lock has a lid 2 mounted on the front surface of an outer box 1 in such a manner as to be openable and closable, a switch 6 for connecting an alarm to a power source and an interlocking mechanism for opening and closing the switch by the opening and closing of the lid are provided in the inner part. An outer hardware 10 which was mounted on the outside surface of a door with a key hole being exposed is integrated into the outer box 1.