A key management box includes a card reader configured to read ID for personal authentication, a data writing unit to write information on at least the ID read by the card reader in an electronic key, a data erasing unit configured to communication with the electronic key and disable the electronic key when the electronic key is determined to be a key on-lending, and a control substrate configured to determine that a lending mode is established when the card reader reads the ID and cause an electronic lock to permit opening/closing of a door and then activate the data writing unit, or configured to cause the electronic lock to permit opening/closing of the door when the data erasing unit determines that the electronic key is a key on-lending through communication with the electronic key while the card reader does not read ID.