To provide a detecting device for vault door locking and unlocking having a simple construction with less troubles.

This device includes an excitation means 10 contributing to the switching of a contact for a switch means 50 connected to an alarm delivery means 70 transmitting an alarm to a monitor center 90 and a switch means 50 for guiding alarm delivery by an alarm delivery means 70 by switching of the contact by this excitation means 10 in configuration.