A home interior monitoring system includes a master device that can wirelessly communicate with at least one electric device installed in an interior of a home and is not connected to the Internet, and a mobile phone terminal that can wirelessly communicate directly with the master device. The mobile phone terminal, in a case of launching an application, sets, to OFF, a connection invalidity flag that invalidates wireless connection to an access point that is not connected to the Internet. The master device outputs an electromagnetic wave for wireless connection with the mobile phone terminal.