A control system transmits, to a remote monitoring server, report data generated based on operation data. The control system includes a facility-device management apparatus that generates report data based on the operation data, and a relay device that communicates with the remote monitoring server via an intra-facility LAN and communicates with the facility-device management apparatus via a connection line. The facility-device management apparatus includes setting means for setting whether or not the report data is to be transmitted to the remote monitoring server, first transmission means for transmitting the report data to the remote monitoring server, and second transmission means for transmitting the report data to the relay device. The relay device includes forwarding means for transmitting, to the intra-facility LAN, the report data received from the facility-device management apparatus.