To solve the problem that there is no alarm issued, for example, in the case where a key is not brought back even after the lapse of a predetermined time from the lending of the key, because a conventional key management unit can hardly cope with the state of the key management unit in accordance with the presence or absence of a key manager.

This key management system comprises a key storage unit and the key management unit. The key management unit determines whether or not alarm starting conditions are satisfied, in a periodic manner or each time notification of information on the presence or absence of the key is provided from the key storage unit. When the key management unit determines that the alarm starting conditions are satisfied, it starts alarm equipment, and makes the alarm equipment automatically give the alarm to an information addressee which is registered in an information addressee registration means.