To alert a person concerned and surrounding persons engaged in construction, to perform monitoring in a dangerous invisible place, and to prevent accidents and crimes, etc.

A device body 1 is attached to a building facility and a structure regardless of a location, an attachment metal fitting is freely attached according to an environment of a site, and since push/pull force is applied to a spread section identification rope, an alarm is issued by an alarm 2 and a buzzer 8, an unsafe action and an unsafe state are stopped promptly, and crash/fall accidents, danger area intrusion and robbery are prevented. In the system, power sources 6 and 10 are duplexed, AC/DC batteries are provided, a buzzer volume adjustment and OFF function 12 and a nut 11 for adjusting tension of the identification rope are provided, the tension adjustment of the section identification rope or the like is facilitated, and since it is a waterproof specification, outdoor attachment for a long period of time is possible. By using the buzzer OFF switch 12, it is usable for alarm display 2 indoors and outdoors and it is useful in an emergency as well.