To prevent cash, a purse, baggage, etc., from being left behind at an article holding part provided at a facility for individuals to be used individually by an unspecified person such as a public telephone, a cash dispenser, a safe deposit box, a public lavatory.

When an article detector 1 detects the existence of an article because the article is actually left behind at the article holding part when a user utilizes the facility for individuals and finishes the utilization, a warning is given from a warning means 2. As the warning is not a message which uniformly and simply calls the user's attention but warns only when an article is actually left behind, the user does not fail to notice the article left behind.