When a security server detects an abnormality in the building by a sensor, the security server sends an abnormality notification mail that has embedded a link to image information shot by a supervision camera upon detection of an abnormality and a mail address of the security server to a portable telephone terminal and in case neither access from the portable telephone terminal to the image information nor a response mail is confirmed, determines that the abnormality mail is not confirmed by the user and notifies occurrence of the abnormality to a security center.