A HEMS controller repeatedly transmits a predetermined signal to a control-target appliance at a set time interval in order to detect a change in a status of the control-target appliance. If the status changes, the HEMS controller notifies a smartphone of the changed status via a server apparatus. In a state where the time interval is set to a first time interval, when receiving a control instruction for controlling an operation of the control-target appliance from the smartphone via the server apparatus, the HEMS controller transmits the control instruction to the control-target appliance. In response to the transmission of the control instruction to the control-target appliance, the HEMS controller changes the time interval to a second time interval shorter than the first time interval.