PURPOSE: To make it possible to enter and leave rooms without bothering a superintendent by providing a utility box to keep key devices making it possible to enter the rooms, an unlocking means to unlock by designating the box and a security releasing means.

CONSTITUTION: A master key or a bunch of keys is taken out from a utility box 10-1, (10-2) or returned bake thereto by designating the utility box 10-1 to open the front door, and a sanitation man can enter and leave the rooms for required tenants. Without taking out an entry key from a module unit 1, a required tenant is designated to release a security state therefor, functions of the utility boxes 10-1, (10-2) are used jointly, and the sanitation man and a superintendent of a building are not restricted by time. According to the constitution, an unattended building having no superintendent as a full timer can be also filfilled.