PURPOSE: To improve crime-preventing safety control by providing a key holding box with a locking device, by providing the bottom section of the key holding box, with a load detector for working with the tare weight of a key, and by setting an alarm for working with the output signal of the detector.

CONSTITUTION: When a resident leaves a building 1 and when a magnetic card 4 is inserted into a second magnetic card reader 14, then by the central processing device 5a of a controller 5, it is discriminated whether the card 4 can be entered into a directory or not. After that, when the directory is identically checked, then the opening or closing door 8a of a key containing shed 8 is opened based on command from the controller 5. After that, when the key of the containing shed 8 is inserted into, then a switch 13 is tripping-worked by a locking device 11, and the electrification of the power source of the electrical equipment 12 of an air conditioner 12a, a lighting equipment 12b, and the like is interrupted, and a locked state is set. Besides, when the resident leaves the building 1 and when the key is contained in the containing shed 8 without being inserted into the locking device 11, then the switch 16a of a load detector 16 is worked, and via the processing device 5a, an audio response device 15 is worked, and audio alarm is generated.