A key box (1) has a housing (10) and a cooperating door (11) which, in combination, form a secured space (9) when the door (11) is closed, wherein the door (11) is locked by means of an electric locking system. The locking system comprises an electric locking mechanism (21), an electronic control unit (22) and a wireless communication unit (23). The electronic control unit (22) is configured to communicate wirelessly with a mobile unit (40) by means of the wireless communication unit (23). The electronic control unit (22) is configured to verify access rights relative to the mobile unit (40) and, if the access rights are authenticated, to cancel the locking effect of the locking mechanism (21). The control unit (22) and the wireless communication unit (23) are accommodated within the secured space (9).