To inexpensively provide a security system having a monitoring function for abnormality in life by providing a means capable of easily and inexpensively discriminating the presence/absence of a resident, integrating the monitoring function for the abnormality in life of the resident into the security system, and sharing one part of detecting sensors or all the detecting sensors.

This system has a security mode setting means 14 for switching an outside security mode, at-home security mode and at-home monitoring mode, a timer 16 for measuring time not to detect the presence of any person in the at-home security mode, a transmission means 18 for reporting an alarm to a prescribed monitoring center by judging the occurrence of abnormality when the timer 16 exceeds a specified time, and a control part 12 for performing various kinds of processings at the time of outside security mode and at-home modes. Thus, the presence/absence of the resident can be easily and inexpensively discriminated, and by sharing one part of detecting sensors 10 or all the detecting sensors, the security system having the monitoring function of living abnormality can be inexpensively provided.