To remove difficulty in mounting for such as a water sensor, to prevent malfunction of such as an infrared sensor or a toilet door opening/closing detecting sensor and to facilitate wiring works.

Brightness and temperature inside a room are detected by an optical sensor 2 and a temperature sensor 3. When the brightness does not rapidly change throughout 12 hours or more or the temperature does not rapidly change throughout 12 hours or more, a safety deciding means 4 decides that there occurred some abnormality to an inhabitant for transmitting a signal by radio to a reporting device 6. A presence/absence deciding device 7 detects that a key holder 9 of an entrance key 8 is inside a key box 10 for transmitting a signal of presence by radio 11 to the reporting device 6. When the reporting device 6 receives the signal of presence and the signal of abnormality, it blows a warning buzzer 12 first then to telephone outside, to blow a buzzer inside the room and to blink a lamp.