The energizing information reception log recorder 204 records a log of reception of energizing information, which is periodically transferred by the adapter 100.

The energizing state log recorder 205 records a log indicating whether or not electric power is supplied to the socket 20 (hereinafter referred to as energizing state log) based on the energizing information received from the adapter 100. That is, the log indicates whether or not the electric circuit of the light bulb 30 is energized, based on an indication that the electric circuit of the light bulb 30 is energized, for one or more of the registered adapters 100 connected to the light bulbs 30.

The monitoring information generator 206 generates monitoring information based on the energizing state log recorded by the energizing state log recorder 205.

The monitoring information transmitter 207 transfers monitoring information in response to a request from the user or the external server 300.

The warning condition fulfillment determination unit 208 determines whether or not a preset warning condition is satisfied based on the energizing state log recorded by the energizing state log recorder 205.

The warning information transmitter 209 transfers warning information to a preregistered destination when it is determined that the warning condition is satisfied.