To make it possible to request confirmation request operation to a user and reliably issue confirmation information.

Provided to a monitor system are a plurality of house alarms that observe environment change, detect abnormality in a monitoring area, and give information in conjunction with one another. When detecting arrival of periodical confirmation request timing, a conformation request processing unit 62 of a house alarm 10-1 issues confirmation request information requesting confirmation request operation and sends a linkage signal showing confirmation request to the other house alarms. When receiving a linkage signal showing confirmation request from the other house alarms, the confirmation request processing unit 62 issues confirmation request information requesting confirmation request operation and issues confirmation request information when confirmation request operation by a user is detected.